Building the Skyline

The Birth & Growth of Manhattan's Skyscrapers

by Jason Barr 1 Comment

Exciting versus Boring Skylines: Which Countries Build Up?

Jason M. Barr and Remi Jedwab                    May 9, 2023

When we think of skyscrapers, we think of the tales of ego-drenched developers engaging in height competitions to claim the prize of “tallest building.” We recall the three-way height race during the Roaring Twenties between the Chrysler Building, the Bank of Manhattan Building, and the Empire State Building.

But despite the tendency to telescope on supertalls and record breakers, they are–statistically speaking–rare. The world record has been broken only 12 times since 1890 and only twice in the 21st century. Hardly a perennial gladiator competition.

For that matter, there are over 44,000 buildings around the world that are 100 meters (~25 floors) or taller. Of those, two out of three are shorter than 132 meters (~34 stories); and 90% are shorter than 170 meters. If you use 55 meters (~14 stories) as a cut-off, 83% are less than 100 meters. In short, the vast majority of the world’s tall buildings are between 14 and 30 stories.

Measuring Skyscraperness

And where are these buildings distributed across the planet? To most people, the answer is obvious. China, the United States, and the United Arab Emirates are the clear winners. Hong Kong is the ultimate skyscraper city. New York and Chicago started the Skyscraper Revolution at the end of the 19th century. And Dubai, with the Burj Khalifa, is the world’s “Blingiest City” –Vegas-on-the-Gulf.

But how much do our perceptions capture what is happening globally? Rich and urbanized countries tend to have more skyscrapers because the economic conditions would favor them. In urban centers where land values are the greatest, developers are incentivized to build tall to make “the land pay.” Businesses prefer to be in their downtown clusters, while residents are eager to live in high-rise apartments near work, amenities, and fun.

So, the strong correlation between an economy’s urbanization and gross domestic product (GDP) and the heights of its tall buildings does not say much about which countries are more pro tall than others. New York, Hong Kong, and Dubai are among the world’s wealthiest cities, so the underlying economics would suggest they “should” have more tall buildings.

Thus, we need to measure the degree to which cities and countries build up, not because of the size of their respective economies but rather despite it.

Record Breaking Skyscrapers. From Left: The Chrysler Building (1930), The Empire State Building (1931), The Taipei 101 (2004), The Burj Khalifa (2010). Sources: Wikipedia.

Countries and Skyscrapers

To answer these questions, we have investigated a data set containing nearly all the world’s buildings that are 55 meters or taller.[1] As a first, raw measure of “skyscraperness,” we added up the total heights of all these buildings for each country and divided them by their respective urban populations. This gives the number of kilometers of building height per million urban residents.

When we do this, the densest tall building country is, in fact, South Korea, with Hong Kong second. Singapore, Panama, and the United Arab Emirates come in third, fourth, and fifth, respectively. (The full rankings are here).

Skyscraperness around the World. Left: Total kilometers of building height (55 m+) per million urban residents for the top 15 ranked countries around the world. Right: Total kilometers (000) of building height (55 m+) for the top 15 countries around the world. Note that South Korea ranks #1 in both categories. When diving by urban population size, China and the U.S. no longer rank very highly. Source: Barr and Jedwab (2023).

The result of this exercise is that the countries that contain the most “exciting” skylines are not necessarily the highest ranked. South Korea “wins” because it focuses on high-rises rather than skyscrapers, though it does have one supertall, the Lotte World Tower at 123 stories, the 5th tallest building in the world.

Where is the United States? It’s ranked 19th. The reason is that while New York and Chicago do much of the “heavy lifting,” most cities house their populations in one-family homes. Simultaneously, suburban office parks are just as common, if not more so, than central city office skyscrapers. States like California and Texas are like countries on their own, but their cities have relatively few tall buildings.

Mainland China ranks 43. Ironically, despite China’s love of tall buildings, the data suggest that it does not “overbuild” relative to its urban population.

A Skyscraper Index

But again, this may not be the right measure. A better indicator is to create an index of skyscraperness based on how much cities build up after controlling for their population, income, and other factors that might directly affect their supply.

The result of this exercise—what we call the Skyline Index—preserves South Korea’s top ranking, but, after that, the rankings change quite a bit. In fact, the second most “tall building” nation is Mongolia, followed by Slovenia and Israel. These countries have more tall buildings than they “should,” given the size of their economies. The big players, like China, the UAE, Hong Kong, and the United States, are nowhere to be found.

The Skyline Index. This graph shows the top 15 countries that “overbuild” tall buildings relative to their population size and gross domestic products. Source: Barr and Jedwab (2023).

By Region

Scaling up to regions, we can look at the 19 United Nations (U.N.) Subregions to get a sense of regional skyscraperness. Regional analysis lets us look for broad patterns by grouping countries with similar cultural and economic backgrounds. When we rank regions by how much they overbuild or underbuild, we find that, in fact, the highest-ranking regions are South America, Eastern Europe and Southeast Asia.

Within Asia, Southeast Asia (which includes Indonesia, Vietnam, and Malaysia), not East Asia (which includes China, Japan, and South Korea), is the highest ranked. In contrast, West Asia, which includes the Gulf nations, is not highly ranked. Within Africa, East Africa (e.g., Kenya and Uganda) and Southern Africa are at the top. For example, Bangkok, Jakarta, Nairobi, and Johannesburg contain many tall buildings given their population size and income level.

Regional Skyline Index. This graphs shows the relative degree to which regions build up or not, after controlling for their populations and GDPs. South America is the top-ranked region. Source: Barr and Jedwab (2023).

Skyline Typologies

What drives such regional differences? To investigate this, we compared relative building stocks in small cities versus large ones; central areas versus peripheral ones; cities’ construction of high-rises (55 – 99 m) versus skyscrapers (100 m+); and the construction of office versus residential structures.

We then created skyline typologies by examining how countries build in these categories. Cities that mostly have office or luxury condo skyscrapers in central districts are defined as capital-oriented central district (CD) skylines—these are the exciting skylines of the world, like Manhattan and Dubai. Cities with residential and high-rise buildings in peripheral districts are defined as population-oriented peripheral district (PD) skylines. These are the boring skylines like Bogota and Rio de Janeiro.

Capital-oriented CD and Population-Oriented PDs make up the majority of the world’s skylines. But this analysis also demonstrates a key point: the most impressive skylines are not necessarily the ones with the densest tall-building stocks. For example, regions like South America and Eastern Europe make up in high-rise volume what they lose in supertall skyscrapers.

Skyline Typologies. This graphs shows the types of skyscrapers that are most predominate for the 19 UN Subregions. Population Oriented (PO)=mostly residential high-rises. Capital-oriented (CO)=mostly offices or luxury condos. PD=Tall buildings mostly in peripheral districts. CD=tall buildings mostly in central districts. Most of the world’s skylines are other POPD or COCD. Source: Barr and Jedwab (2023).

Explaining the Variation

But what might be driving cities to have one typology over another? We believe there are four possibilities.

The first is land-use regulations. Many cities regulate building height in the name of reducing the negative “externalities,” such as traffic congestion and shadows. Another form of regulation is historic preservation, as residents may demand the protection of their historical buildings or height limits outside of these neighborhoods to preserve sight lines.

Another possibility is the nature of land ownership. In many older, more developed nations, land ownership can be highly dispersed among many owners of small lots. On the other hand, across China, municipal governments own vast tracts of underdeveloped land that they sell to high-rise developers to generate large housing estates. In developing nations, land assembly, particularly in regions with weak property rights, might hinder tall building construction because ownership claims are vague or diffused.

Lastly is the preference for high-rise living. Some societies may have a cultural preference for living in structures with few stories or individual houses, such as the U.S., where a free-standing house is seen as the norm. On the other hand, residents in Asian countries such as China, South Korea, and Japan see high-rise living as the norm and most desirable.

Typology Drivers. Left: Skyscraper Index values versus average maximum floor area ratio for 19 U.N. Subregions. Right:  Skyscraper Index values versus share of tall buildings that are residential. The positive correlations found in both graphs suggests that regions that build up have less stringent zoning regulations and prefer high-rise living. Preferences and zoning regulations appear to be the most important determinants of why skyline types vary around the world. Source: Barr and Jedwab (2023).

Findings

To this end, we use collected data to evaluate these four theories. We looked at the relative ages of cities and the number of world heritage sites, to gauge the difficulty of amassing lots (more historical cities would presumably have more diffused ownership) and the desire for preservation, respectively. We also looked at the average allowable floor area ratios (FARs) across regions, which measure how much building space can be provided and thus indicate the stringency of regulations. Finally, we also looked at the share of residential structures as a measure of the preferences for high-rise living.

The two most important determinants of why regions build upward or not are their FAR stringencies and their preference for residential high-rises. Likely the two things are not independent in that when citizens want to live in tall buildings, local regulations are likely to be less stringent.

The Boring Truth

When looking at global skyline characteristics, focusing on exciting skylines is misleading. About 70% and 80% of tall building heights in the world come from high-rises below 100 meters (not skyscrapers) and residential towers (not office buildings), respectively. Thus, many skylines visually appear more prominent internationally than they are after controlling for standard demand and supply variables. Hence, boring skylines are more numerous worldwide, despite suffering from a visibility problem.

So when you look up at the Empire State Building or the Burj Khalifa, remember that their heights don’t represent what’s actually happening on the ground.

 

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[1] Information about the dataset and the analysis can be found in our 2023 paper, “Exciting, boring, and nonexistent skylines: Vertical building gaps in global perspective” in published in Real Estate Economics.

by Jason Barr 1 Comment

Clouds in Your Coffee? Skyscrapers and their Symbolic Heights

Jason M. Barr          January 20, 2021

You’re So Vain?

On January 4, 2010, the Burj Khalifa officially opened its doors. At 828 meters (2,717 feet) it became the world’s tallest building by a long shot. It overtook the previously tallest building, the Taipei 101, by 302 meters (991 feet). The only rub: Much of Burj is empty space—the top third is a 243-meter (797-foot) spire—where no human will likely ever work or live.

The difference between the actual or architectural height (excluding TV and radio antennae) and the highest occupied floor is what the Council on Tall Buildings and Urban Habitat (CTBUH) has dubbed “Vanity Height.” They originally coined the term, with tongue in cheek, because some developers—presumably—have added a decorative element simply so they can brag about having a taller building. For the CTBUH, the de facto arbiter of official building heights, these elements create a conundrum.

The most famous recent examples of Vanity Height are the Petronas Towers (1998) and One World Trade Center (2014). When completed, the Petronas Towers took over the title as the world’s tallest building (until 2004) because of its spire. The highest occupied floor remains well-below the previous record holder’s top floor, the Willis (Sears) Tower (1974). To many, it seemed that to beat the record, you simply build a tall skyscraper, attach a glorified pole, and declare victory.

Similarly, One World Trade Center, in New York, is only the tallest building in the Western Hemisphere because of its 154-meter (505-foot) spire, which looks more like an antenna than an artistic statement. Its sole purpose, it appears, is to allow the skyscraper to rise 10 1,776 feet (541 meters), as a symbolic gesture to the birth (and hopefully continuance) of American Democracy.

Space Wasters?

In 2013, the CTUBH published an article discussing so-called Vanity Height. They showed that among a crop of 200-meter or taller buildings, several notable examples had spires or other architectural elements of at least 95 meters (312 feet), comprising 25% or more of their respective total heights. The article tickled the funny bone of the press, who went on a reporting rampage, producing such splashy headlines as, “Space-wasting ‘vanity’ skyscrapers revealed,” and “44 of the world’s 72 tallest buildings are cheating.”

Assumptions

While the 2013 article was meant as a jocular jab at some developers, the phrase has remained in the public sphere because it feeds the belief that skyscraper builders are only concerned about self-glorification and are unconcerned about other mundane things like profitability or urban well-being. The phrase “Vanity Height” implies that all structures with large vertical voids are—by definition—ego-borne. But this belief obscures other reasons for what is happening up top. The drivers and impacts of this extra height are more complicated.

Another implicit assumption is that skyscrapers are getting “vanier”—that builders are adding more of it now than in the past. The phrase fuels the idea that developers in the 21st century are engaged in an arms race to claim the prize. This suggests a degree of dissipative or wasteful competition—that by adding height to stand out, developers are spending resources to satisfy themselves, with no larger benefit to society. To what extent are these assumptions true? The answers will be revealed below when we look at the data.

Vanity Heights? Despite the controversy, the degree of “space-wasting” height among the world’s tallest buildings varies widely. The Twin Towers and Willis (Sears) Tower have virtually none, while more recent structures add a varied amount (ignoring antennae).  From Left: Burj Khalifa (2010), Petronas Towers (1998), Taipei 101 (2004),  Willis (Sears) Tower (1974), Twin Towers (1972/3). Note that the buildings are not to relative scale.

From “Vanity Height” to “Symbolic Height”

Tall buildings serve many purposes beyond providing space for people to work, live, or play. They also convey information: Big corporations like to be in iconic buildings because they signal something about their business, such as their profitability or trustworthiness. Corporate headquarters are part of the larger need for branding because branding gives a certain level of assurance about what consumers get when they buy a company’s products. More broadly, companies that have national or international ambitions find they need to be in skyscrapers to signal their ability to compete in the global marketplace.

Cities like to have iconic structures because they increase tourism, foreign direct investment, and advertise that the city is a dynamic urban center. Architects, when designing tall buildings, also have multiple goals. They want to not only deliver an iconic structure to their clients but also seek to make their buildings aesthetically pleasing and meaningful. To architects, “Vanity Height” is often shorthand for the design up high.

I asked architect Ro Shroff, of 3MIX, who is involved in several tall building designs around the world, his thoughts:

I generally concur with the notion of Vanity Height, and it has almost become a de rigueur methodology for most architects, to “enhance” the proportions and appearance of the tower, and create some identifiable iconography to differentiate from other skyline cacophonies. This is accomplished either by extending the façade as a screen to hide the rooftop equipment or by creating unoccupiable voids, vertical spires, spiraling crowns or glowing lanterns, not too dissimilar from the design intents of the Empire State and Chrysler Towers in the 1930s.

Then there are developers who may want to have icons for their personal satisfaction or bragging rights. But this leads to an important question: Where do beauty and iconicity end and vanity begin? This is inherently unanswerable. Shroff adds, “Hopefully and presumably, such vanity exercises in ‘irrational exuberance’ by the architects or developers are also countered with fiscal responsibility, maintenance economics, and other checks and balances.”

The Information

The bottom line, however: We cannot say much about so-called Vanity Height by looking at a few buildings. We can cherry-pick and shout-out the ones that appear most egregious.  But, as I show below, the data strongly support that relatively few buildings are as bad as we think.

This leads me to propose a new name for this type of height: Rather than Vanity Height, we should call it Symbolic Height, because it is height added to convey information of some kind.[1] This information can be literal, like broadcasting the name or logo of a corporation, or abstract, such as an aesthetic design or sculptural elements.

Early Examples of Symbolic Height in New York City. From Left to Right: World (Pulitzer) Building (1890) with decorative dome; Tribune Building (1875) with decorative tower; Singer Building (1908) with occupied tower; Empire State Building (1931) with mooring mast/spire. Note: Buildings not to scale.

A Brief History of Symbolic Height

Symbolic Height has a long history and is older than the skyscraper itself. A review of this history demonstrates the multiple purposes that tall structures serve, the different types of information that they broadcast, and the benefits of the voids up high.

We can think of gothic church spires or old city hall clock towers. Sure, their heights were meant to announce the power of the institutions that created them, but they also served other purposes, especially related to telling time—church bells and clocks to telegraph the hour of the day. They also provided locational beacons—in a low-rise city, people could head for the center by moving toward the structure rising in the skyline.

Then there are towers, arches, and obelisks, built with no other purpose in mind than as symbols (with the occasional observation deck thrown it). Despite their “useless” objectives, do we complain that the Eiffel Tower is too tall or that the Washington Monument is a waste of resources?

When the building technology to go tall was perfected, developers—be they corporations or individuals—realized they could add extra heights to convey information about the occupants or builders. The first record-breaking buildings in New York, such as the Tribune Building (1875) or World (Pulitzer) Building (1890) added decorative towers or domes to raise themselves above the fray and to express the power of their business or industry.

Early developers also added occupied towers. Both the Singer Building (1908) and Woolworth Building (1913) are large, bulky office building with extruded towers, which also play the role of Symbolic Height, though, in these cases, they also provided office space. It also shows that not all Symbolic Height is empty space or decorative spires.

And yes, developer and ego-based competition has driven buildings to be taller than they would otherwise be. The developers of the Empire State Building (1931) added a 61-meter (200-foot) dirigible mooring mast to lock in the world record, while Walter Chrysler added the 56-meter (185-foot) stainless steel spire—“the Vertex”—to beat out the Bank of Manhattan Building (1930) at 40 Wall Street.  However, without this competition—this “Vanity Height”—the city would feel a little emptier.

There are examples around the world of practical uses for the voids up top. The Ping An Tower, in Shenzhen, contains a mass tuned damper that helps stabilize the building against wind forces. In the observation deck of the Shard, one can look up into the “Vanity Height,” hovering above; the experience helps enhance the pleasure when viewing the London skyline.

The Opposite is Also True

Not every record breaker or supertall has Symbolic Height. Both the Twin Towers (1972/3) in New York and the Willis (Sears) Tower (1974) have near-zero additional space above the top floor. Architectural modernism after World War II was a movement away from overt expressions of decorative height. The idea was that record breakers speak their intentions simply by being tall towers. Today, the view of “Billionaires Row” from Central Park shows wide architectural variety on top. 432 Park Avenue—like the former Twin Towers—just stops, with no decorative elements. A few blocks away, the rising Steinway Tower has a tapering, almost two-dimensional, 90-meter (295-foot) crown. Vanity or art? Perhaps both.

Symbolic Height: A Look at the Data

Despite some interesting examples here and there, we cannot say much about Symbolic Height, on average, because no one has analyzed more than a handful of buildings. To this end, using the CTBUH database of tall buildings, I have performed a statistical analysis to look at the patterns of Symbolic Height for about 2,000 skyscrapers worldwide.

The goal is to answer a set of related questions: Is Symbolic Height—the difference between the architectural height and the height of the highest occupied floor—a systematic part of the tall building universe? What has been happening to Symbolic Heights, on average, over time? Has it been rising, as is commonly assumed? Does the data support the idea of dissipative or wasteful competition among developers? And lastly, are China and the United Arab Emirates (UAE) the worst offenders, as people commonly assumes? (Data sources and statistical results are here.)

Symbolic Height Around the World

The answer to the first question is “no.” The average Symbolic Height, as a fraction or percent of total height, for buildings around the world of at least 100 meters is about 10% (with a median of 8%). In other words, on average, Symbolic Height represents only 10% of the total structure’s height, which suggests it typically plays a very small role. For supertall skyscrapers of 300 meters (984 feet) or taller, that average is still quite low at 12% (median of 9.7%).

This is not to imply that all tall buildings have a Symbolic Height of only 10%. There is a degree of variation—mostly on the low end. 75% of 100-meter or taller buildings in the database have a Symbolic Height of 12.5% or less. Only 5% have a Symbolic Height above 22%. For those at or above 300 meters, the numbers are similar: 75% of these buildings have a Symbolic Height of 18% or lower. Only 5% have 28% or higher.

Variations in Symbolic Height. Left: Relative frequency histograms (%). The blue line gives the distributions for Symbolic Height for 100 m+ buildings in the sample. The orange line gives the distributions for 300 m+ buildings. For example, about 18% of 100 m+ buildings have Symbolic Height around 8%. Right: Cumulative relative frequency histograms. The blue line gives the percent frequency of  Symbolic Height at or less than each value for 100 m+ buildings. The orange line is for 300 m+ buildings. For example, about 80% of 100 m+ skyscrapers have Symbolic Height less than or equal to about 13%  Source: here.

Symbolic Height Over Time

What about over time? Is Symbolic Height growing? Again, the answer is “no.” Using this data, I have created a Symbolic Height Index (analysis here), which gives the average Symbolic Height around the world each year, relative to the long run global average of 10%, after controlling for building location and use. The results suggest, first, that is no long run trend, but rather is cyclical. The Index peaked in the  1997 (a year when no new world record breakers were built), before Asian countries dove into the skyscraper game. As places like China and the UAE ratcheted up the tall building construction in the 2000s, the Index moved up until 2006 (before Global Financial Crisis) and has been falling ever since.

The Index also reveals relatively muted movements. Even in robust times, when more developers were adding extra height, the highest amount above the average was 7 percentage points. In other words, the data suggest that Symbolic Height is based on fashion or tastes, rather than developers need to systematically outdo each other. The findings also suggest that “irrational exuberance” is punished in the long run.

Global Symbolic Height Index. This index gives the percent of Symbolic Height relative to the long run average (10%) for each year from 1968-2018. Note this index is an moving average (3 years) from 1966 to 2018, with 1982=10 (the long run average). Source: here.

Symbolic Height by Country

Which countries are the most egregious on average? The results of the statistical analysis are surprising. Among the 64 countries that have built at least one skyscraper since 1966, the top three are Ethiopia, Kenya, and New Zealand, with average Symbolic Heights of at least 25%. The UAE, China, and the United States are in the middle of the pack.

Just focusing on countries that have built at least ten skyscrapers, the UAE and China rise in the rankings. But their averages are still not that far above the global average of 10%. In short, when it comes to Symbolic Height, these countries about average. Among the public perception, China and the UAE appear to be “bad” because there are a handful of notable extreme cases. However,  by focusing on those, we lose the skyline for the skyscrapers.

Symbolic Height by Country. Left: Rankings and average Symbolic Height for selected countries based on 64 countries with at least one skyscraper. Right: Rankings and averages for selected countries based on 27 countries that have at least ten skyscrapers. Source: here.

Variety is the Spice of Life

Given there is a certain cache to having a nominally taller building, the “stick-a-pole-on-it-and-declare-victory” type skyscraper is not likely to go away anytime soon. But a review of the broader evidence suggests that these types of buildings are the exception rather than the norm. There’s also little evidence that developers are engaged in a dissipative battle royale to beat each other for the title. So what if there are a few too-tall buildings out there? The variety alone makes it worth the cost.

 

Thanks to Maria Thompson for editorial assistance.

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[1] Note that in my book, Building the Skyline (2016), and a previous blog post, I defined Symbolic Height in a slightly different manner. There, Symbolic Height was the difference between the actual or architectural height and the profit maximizing or economic height based on revenues and construction costs. Thus, Symbolic Height can include extra floors above the profit amazing height in addition to decorative elements or spires. Given that the two definitions of Symbolic Height are likely to be fairly close, on average, it can be a reasonable substitution for the definition of Vanity Height.

by Jason Barr 11 Comments

In a City FAR, FAR Away: Building Height Regulations and Their Impacts

Jason M. Barr      March 17, 2020

Your New Job

Imagine the governor of your state announces that she is going to create a brand-new city out of whole cloth. The state has purchased 200 square miles (519 km2) of farmland (around the size of Chicago) and will begin auctioning off lots for development. The governor is working with officials to build the transportation and infrastructure network. But she has turned to you with a critical mission: to formulate the regulations about building heights. Your job, as Chief Building Heights Planner, is to develop a series of plans about how dense or tall the structures can be throughout the city.[1] Where should you begin?

Options

You can think of the possibilities as existing along a continuum. On one side is to write no rules and allow buildings to be as tall or as dense as developers want. If someone builds a 100-story skyscraper in the middle of a leafy residential neighborhood, so be it. If builders cover 100% of the lot and put their neighbors in darkness, that’s okay too.

The other extreme is to order the city entirely. Say you build a 3D model in your office and arrange the exact scale, density, and height for every structure. There can be no deviation. Building #1 must go here and must be so many stories. Building #2 must go there and have exactly so many floors, and so on.

Option three, of course, is somewhere in between, where you designate some rules on height and density, and let the real estate community figure out the rest. But even within this option, there’s a wide spectrum. Do you set limits for everyone? Do you restrict hieght in some places but not others?

What Do these Four Buildings Have in Common? All of these Brooklyn structures have a floor area ratio of 3. Clockwise from top left: 181 Clermont Ave (2007, 6 floors), 761 Atlantic Avenue (1974, 31 floors), 109 3rd Avenue (1900, 4 floors),  1630 41 Street (1926, 4 floors). Source: OASIS NYC Map.

How FAR Can You Go?

After doing a little research, you find one popular regulatory tool is to limit the so-called floor area ratio (FAR).[2] The FAR dictates how much building space can be constructed based on the lot size. For example, in an older (pre-car) dense apartment-based neighborhood, the rules might specify a maximum FAR of 3. This means that on a 2,000 square foot (186 m2) lot, the most a new building can have is 6,000 square feet (557 m2) of living space.

If we assume, for example, that each household in the building rents 600 square feet (58 m2), then that building will have ten units. A FAR increase to 4, means the structure can be 8,000 square feet (743 m2), with 13 units. If each apartment, on average, holds two people, the FAR-3 building has 20 people, and the FAR-4 building has 26 people.

Building Heights

FAR limits say little about building heights directly. In a FAR-regulated city, the height is chosen by the developer, based on what works best for her. In the FAR-3 example, she can build a three-story building that takes up the entire lot, or she can erect a six-story building that covers only half the lot. Yet both will hold the same number of people.

Thus FAR limits mean that building bulk and height are substitutes—the taller the building goes, the narrower it must be, with more open space surrounding. This strategy presumably mitigates the negative impacts of tall buildings, such as shadows on neighboring properties. For these reasons, FAR regulations are popular among planners. They are a simple way to reduce the density of both people and buildings.

Wheel of FARtune?

By how do planners choose the “correct” FAR values across the city? The answer is: they just pick numbers that seem right—usually some higher numbers in the central core (say 8 to 15), medium numbers in the dense residential rings (say 2 to 4), and much smaller figures further out (typically one or less). These values are often based on what “feels” appropriate, or are politically salable, and are not tied to any economic research that attempts to weigh the costs of restrictions versus their benefits. A survey of maximum FARs in central cities around the world shows that planners have chosen a wide range of numbers. Their arbitrariness is also supported by the research discussed below.

Average Maximum Allowable Floor Area Ratios Versus Distance from City Center for New York, Chicago, and Bengaluru. For each city, I took the average of the maximum allowable FAR for buildings in 1 kilometer rings from the center city. In New York, the average allowable FAR within 1 KM of the center is about 9. For Chicago, it is about 12, and in Bengaluru it’s about 1. Sources: New York: NYC PLUTO, Chicago: Building footprint shapefile, Bengaluru: Breuckner and Bertaud (2005). Note: Average FARs were not weighted by lot size.

FARnomics: The Economics of FAR Regulations

Recently, economists have begun to question the wisdom of choosing urban FARs based on planners’ notions of what constitutes the “good” city. Economic analysis about FAR regulations starts with a series of questions: What would density look like without any FAR limits? Under what conditions would restrictions help improve city well-being? When would FAR restrictions make things worse?

The Order without the Design

As Alain Bertaud discusses in his 2018 book, Order without Design: How Markets Shape Cities, a bustling metropolis without any FAR restrictions will generate a natural order. In the central city, where land values are high, developers will be incentivized to provide taller builders on relatively small lots. As land values decline moving away from the center, buildings will get shorter, on average.

A well-functioning land market will also create a predictable pattern for population density. Near the center, where land is expensive, households will live in apartment buildings. Further away, where lots are cheaper, people will occupy larger houses. Thus, density will be high near the center and fall from there. This outcome is based on the choices of households and represents what they prefer—better accessibility to the center versus more housing and open space further away. The price of land is the nexus between what households want and what kinds of real estate will be constructed. Overly burdensome regulations will distort land prices and prevent them from efficiently allocating housing demand with housing supply.

Key Assumptions

The optimality of this natural order is based on a few assumptions. First is that there are no negative spillovers or externalities from this arrangement. That is, the tall buildings in the city don’t create excessive shadows, promote hyper-congestion, or generate undue health or social problems. Additionally, economists assume that residents or visitors are indifferent to the building designs and shapes that would spring up when the real estate market is relatively open. Tall or dense buildings, it is assumed, don’t offend people’s aesthetic sensibilities.[3]

The presence of these possible harmful elements has been the driving force and justification for imposing FAR restrictions. City officials argue they are necessary to relieve congestion, provide open space, improve urban health, and make the city “beautiful.” But the economist would respond: if this is so, what are the “right” set of restrictions (assuming that restrictions are the best way to solve these problems) that best balances the trade-offs. The truth is, as of this writing, no one knows. The proper calculations have yet to be done.

The Case of New York

Take New York City as an example. The city’s FAR-based regulations were enacted in 1961. They were designed to reduce density as compared to the 1916 zoning codes, which were seen as not being restrictive enough. While small FAR changes (rezonings) in different neighborhoods occur from time to time, there has been no systematic change in the regulations in over half a century. In other words, the same FAR codes, more or less, are in effect today as when John F. Kennedy was President and when The Andy Griffith Show was one of the most popular TV shows in the nation. (If you’re young enough not to know what I’m talking about then I think I’ve made my point.) Once FAR regulations are imposed, they are nearly impossible to dislodge, despite mounting evidence that they are harming the city.

Furthermore, in 1961, when these regulations were set, planners with who felt that promoting the tenants of modernism was surely the path to urban utopia. Clearly, by 1975, when New York City was ready to declare bankruptcy (see “Ford to City: Drop Dead”), utopia was on the minds of few. Sticking with these outdated zoning rules is like trying to use a Commodore 64 computer to process “big data” data.

Estimating the Impacts of FAR Regulations

Recently, however, the urban economist Jan Brueckner, of the University of California-Irvine, and co-authors have studied the impacts of FAR restrictions around the world. His research asks the question: What are the costs of excessive FAR restrictions, imposed in the name of improving the common good?

Bengaluru (Bangalore)

Indian cities have some of the lowest central-city FAR values in the world. Planners have established them, evidently, as a backdoor way to impose their notion of a better city, and because officials couldn’t provide the city services needed to support a dense urban core. As Brueckner and Bertaud (2005) write, “It is believed that ‘excessive’ density results in a loss of environmental quality and increased traffic congestion. In addition, higher densities would place greater demands on urban infrastructure, which Indian cities, plagued by weak technical capacities and inadequate tax revenue, feel ill-equipped to provide at appropriate levels.”

Unlike New York (with a maximum central-city FAR of 15), and Shanghai (with a maximum central-city FAR of 8), Bengaluru has a central-city FAR capped at less than 1.5. This number is considered reasonable for a suburban residential neighborhood of garden apartments, but absurdly low for a central business district in a metropolis with 8.4 million people.

Maximum Allowable Floor Area Ratios in Central Areas for Selected Cities. Source: Brueckner and Sridhar (2012).

In their paper, Brueckner and Bertaud explore the economics of these excessive restrictions. They demonstrate that these FAR limits promote denser development in the suburbs than would otherwise be the case, and create larger, more sprawling cities. The attempt to limit building heights in the center to reduce congestion inadvertently creates more congestion by promoting more driving. If we think about the (lightly-regulated) city as a block of clay. The draconian FAR restrictions are tantamount to smashing the clay. The result is a flatter, wider entity.

They perform some calculations for Bengaluru, and find that the excessive sprawl reduces average household income from extra commuting by 2%. It’s also worth noting that, in recent years, Bengaluru has achieved an international reputation as a tech hub. Limiting densities may have other consequences, such as reducing the opportunities of firms and workers to interact and learn from each other. These restrictions are likely reducing citywide productivity than otherwise.

101 Indian Cities

In a 2012 paper, Brueckner and his collaborator, Kala Seetharam Sridhar, investigated the impact of FAR restrictions on urban sprawl for 101 municipalities throughout India. First, they find a wide distribution of maximum central-city FARs. The lowest city has 1, and the highest has 4.125. The average city in the sample has a central-city FAR of 2.87. Again, compared to other cities around the world, these figures are low.

They next study how these FAR restrictions impact the total land area of municipalities, which is a measure of urban sprawl. Based on their analysis, they conclude that if the average city in India raised its central-city FAR by one unit (e.g., go from 2 to 3), the, it would need 20% less land area to hold the same amount of people. Or, on the flip side, on average, a city that decides to lower its central-city FAR by one is generating an increase in its land area by 20%.

Land Values in China

A well-functioning land market is the main means by which the city orders itself. If land values rise at a specific place, it signals that the residents want taller buildings. If FAR regulations are overly tight, they can lower the value of land, which will then generate buildings that are economically “too short,” denying residents the opportunity to live and work in the location of their choice.

Brueckner, and his co-authors, Shihe Fu, Yizhen Gu, and Junfu Zhang, study the land market in China. Unlike the U.S., there is no private property. Instead, all the urban land is “owned” by the respective municipal governments, who sell long-term leases to developers (70 years for residential and 50 years for commercial). The revenue from these land-leases is used to fund infrastructure and other government projects.

Because municipal officials control this land, they can impose FAR regulations on the developers when they win the right to build. We tend to think of modern Chinese housing as mostly dense, high-rise apartments. This is true, but municipal officials frequently require developers to adhere to relatively low FARs of between 2 and 3. The effect is to create a Corbusian city of tower-in-the-park complexes.

Findings

To study the question of how these FAR restrictions impact land (lease) values, they constructed a very large data set with over 50,000 transactions across more than 200 cities from 2002-2011. Each land-lease transaction also includes the maximum FAR requirement. Across cities, they find that the average residential FAR is only about 2.4.

The authors also find that the higher the FAR restrictions, the greater it reduces land values. Loosening these restrictions would allow land prices to more accurately reflect the benefit of various locations throughout the city. The results suggest that the current FAR values are actually not allowing central locations to be as dense as residents would want.

The Trade-offs

Since Chinese officials lease the land, one would think they have the incentives to provide even looser FARs to increase their revenue streams. However, local leaders must balance the revenues from these land leases with the costs of building infrastructure. So the FAR restrictions may not only be related to notions of sound design principles but also limiting urban density growth to something that will not overly burden the current level of infrastructure. Or, as Brueckner et al. hypothesize, “In this sense, local officials behave as net revenue maximizers, taking into account the public costs associated with land development into account.”

However, if city size or budgetary issues were important than the data would show a relationship with FAR restrictions. But, based on their analysis, they do not find evidence that this is so. Instead,  they find little explanation for FAR stringencies across China, aside from the fact that places with ancient historical sites are stricter. Their results seem to indicate that FAR limits are based on the preferences of city officials rather than on underlying economic principles.

High-rise living in four Chinese cities. Clockwise from top left: Shenzhen, Changchun, Shanghai and Hong Kong. Photos by Jason M. Barr

Land Values in the United States

Brueckner and his co-author, Ruchi Singh (2020), study land values and FAR stringency across U.S. cities. The lower the average allowable FARs, the lower the land values are likely to be, and hence the greater is the “gap” between what residents want and what developers can supply. In particular, they investigate how FAR regulations impact land prices in New York, Chicago, Washington DC, Boston, and San Francisco from 2000 to 2018.

Their analysis allows them to estimate the gaps. They find that New York City is supplying only about 70-77% of the demand. For Washington DC, this number is between 60 to 72%, which makes sense given that DC also has height caps. Boston is supplying around 78 to 83%. And Chicago is at 92 to 94%.

Interestingly, they find that San Francisco’s gap is only between 90 to 93% of what the market wants. Their findings are likely being driven by the relative stringency in each city’s central business district. The demand to live and work in Manhattan is quite strong.[4] Unlike San Francisco’s business district, which “competes” with Silicon Valley, Manhattan has few direct local competitors for its financial and tech services. Similarly for Chicago and Boston.

What Would you Do?

I asked Professor Brueckner to summarize the findings from his body of work. He indicates that, in short, city planners should be careful for what they wish for. He says,

FAR limits reduce housing supply, raise prices and lead to longer commutes. If there are no good reasons for the restrictions, such as better neighborhood ambience, the outcome is a loss for city residents.

As Brueckner’s research shows, the path to getting things right begins with measuring the costs of excessive restrictions. Not going too far with FAR stringency can help a city reduce the negative impacts of density, without eliminating or reducing its benefits. And now, with this in mind, what have you decided to do in your role as Chief Building Heights Planner? If you want to take a look at my planning ideas, you’ll have to stay tuned for a future post on the subject.

 

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[1] You will be part of a team that is developing other rules, including building codes, requirements for health and safety, as well as regulations about land uses. Your decisions will be made in consultation with them.

[2] “Plot ratio,” “floor space ratio,” “floor space index,” “gross plot ratio,” and “site ratio” are other terms also used to designate the FAR.

[3] To the best of my knowledge, there is little research on how residents feel about different kinds of architecture, building shapes and arrangements, and their willingness to pay to be in these neighborhoods. Architects and planners, who have strong feelings about what is right and good, are usually the ones, along with politicians, writing the rules about building heights and densities. There is research to support the notion that walkability and mixed uses are good for residents’ well-being. These findings suggest that there is too much automobile usage and too many zoning restrictions. Good policies can reverse be undone by them as well.

[4] A similar 2019 study for New York City was performed by Brueckner’s student, Byunggeor Moon. Here Moon did the analysis with properties bought to be torn down, rather than vacant lots as in Brueckner and Ruchi (2020). Moon’s findings compare similarly to those of Brueckner and Ruchi.

 

 

by Jason Barr 3 Comments

The Technology of Tall (Part II): The Need for Speed

Jason M. Barr    September 24, 2019

Note this is Part II of an on-going series on the evolution of skyscraper technology. The rest of the series can be found here.

The Chicken or the Egg?

What came first: building height or elevator speed? The history of skyscrapers brings us to a kind of chicken-and-egg conundrum. Does the drive to build tall come first and then fast elevators come next? Or do rapid elevators show what’s possible and then developers exploit them to go taller? While I don’t think there’s any way to answer this question, we can look at the history of the elevator to get a sense how this co-dependency has evolved.

We can say for sure that there is a symbiotic relationship between building height and elevator speed, and together they have enabled cities to grow upwards and hold more people and businesses. Ironically, elevator speed history emerges out of a strange paradox. People are willing to spend an hour or more commuting each day—idling in traffic or dawdling on trains—but when they get to a building, they expect to get from the ground floor to their destination in less than two minutes. It’s the quest for convenience, as much as speed, that has driven the technology forward.

The Birth of Vertical Transportation

Modern elevators are products of the Industrial Revolution, and were first installed in factories, mines, and warehouses. By the 1830s, for example, they were in numerous British textile mills. By the 1840s they were used for passengers. Bunker Hill Monument in Boston, erected in 1842, had a steam-powered lift to take visitors to an observation deck. Wealthy people started putting them into their homes in the 1850s. The first commercial elevators seems to have been installed in New York City before the Civil War. The two earliest examples are the 5-story Haughwout Building (1857) in Soho, and the Fifth Avenue Hotel (1859) at Madison Square Park. Over the ensuing decades, inventors and entrepreneurs continued to advance the art and science of elevatoring to make them faster and safer.

The Safety Break?

The conventional story regarding the elevator revolution begins in 1854. In that year, in New York’s Bryant Park, the Exhibition of the Industry of All Nations—housed in a specially-constructed “Crystal Palace”–demonstrated the world’s cutting edge technology. One vendor present was Elisha Otis. He was showcasing his elevator prototype. In front of large crowds, he climbed onto the platform and hoisted it up a story or so. And then–dramatically–cut the rope holding it in place—producing terror that it would crash. And yet, it did not. The elevator hardly moved. His new safety break kicked in and rescued him from injury and obscurity. Since that dramatic display, the story goes, the elevator’s success shot upwards, now that fear of free-falling was gone. This story has been repeated ad infinitum as the pivotal moment for elevators and skyscrapers.

A Drawing of Elisha Otis Demonstrating his Safety Break to the Public in 1854. This drawing is widely circulated as “proof” that, until the public saw Otis’ safety break in action, they were afraid of elevators. However, according to author Andreas Bernard, this drawing was produced in 1978 in celebration of Otis Elevator Company’s 125th anniversary in 1978. It was an imagined recreation of  past events and helped fuel the idea that Otis was the keystone in the elevator revolution. Image source: Wikipedia.

Myth Busting

Yet according to Andreas Bernard, author of the 2014 book, Lifted: A Cultural History of the Elevator, the story is not so simple. His search for contemporaneous reporting on this “viral” moment came up short. In fact, he finds, at the time, nary a mention in the press. He argues that for such a seemingly pivotal moment in history, hardly anyone seemed to care. He writes,

In the major American daily newspapers and magazines, the 1854 event showed up only in two marginal locations. In addition to the Scientific American article, a brief report appeared on May 30, 1854, in the New York Daily Tribune, which mentioned the daring of the inventor “who, as he rides up and down the platform occasionally cuts the rope by which it is supported.” No further contemporary traces can be found (just as there were no obituaries of Elisha Otis in 1861). Thus it is no exaggeration to say that the demonstration in the Crystal Palace, that “authentic great moment in architectural history,” went almost completely unnoticed by the public.

The story, evidently, is another case of history being written by the winner. Thanks to the diligence of Otis and his offspring, his company went onto to be one of the largest manufacturers of elevators in the world. In 1911, Elisha’s son Charles set out to “correct the record” about elevator history by writing his version of the events, and which minutely chronicled the display in the Crystal Palace. As Bernard writes,

The influence of … [Charles Otis’] text on the historiography of the elevator is obvious from the fact that after 1911, there was hardly a mention of the elevator’s origins that did not begin by repeating the story of the event in the Crystal Palace.

The First Skyscraper?

As a side note, this story has a familiar ring in regard to the world’s first skyscraper. The conventional wisdom is that it was the Home Insurance Building in 1885, designed by William Le Baron Jenney. But this notion seems to have been the product of Chicagoans winning the battle of historiography. The Home Insurance Building, while novel, could not, by today standards be fully described as a “skyscraper” in that it was not fully iron (or steel) skeletal structure.

At the time, many architects and engineers were developing technologies and methods in parallel. In the years after the first skyscrapers emerged in Chicago and New York, there was a battle within the community to claim the prize of “First Skyscraper.” Jenney argued it was his structure; while New York’s Bradford Lee Gilbert said his Tower Building (1889) was first. Others also offered proof they were the true innovators. In the end, through good marketing, Chicago remains the winner in our minds, but this claim highly debatable and far from conclusive.

The Birth of the Rent Premium

Once vertical transport revealed itself to be practical, however, another revolutionary moment was created. Likely, for the first time in human history, was an inversion in the economic and social value of higher floors. Before that, when climbing was the only way up, the top stories were naturally hard to get to. No one wants to climb more than a few floors; as a result, the highest floors were rented to those with the lowest ability to pay. Offices used them for storage or for their low-level clerks.

Rent Premium in 1900 versus 2019. Left: Rent ($ per room) for walk-up apartment buildings versus floor height in the Lower East Side of Manhattan in 1900. Right: Estimated sales price ($ square foot) versus floor height for luxury condos at 217 West 57th Street. The key takeaway: without elevators the higher floors were worth less to tenants because of the trouble of climbing stairs. Sources: Left: See Building the Skyline. Right: See Skynomics Blog post.

In a way, the elevator created treasure in the sky. Because vertical movement was fast and cheap, it generated a rent premium for the higher floors. That is say, the amount of rent paid, per square foot or meter, was higher as one rose up. Today, that premium in New York City is between 0.5 and 1% per floor. In other words, prices on 30th floor of a skyscraper might rent for up to 20% more per square foot as compared to the same space on the 10th floor.  Developers realized if they could get their building occupants up there, they could reap more profits. And the race for height was on. This rent inversion was first noticed in New York City in 1870, when The Equitable Life Assurance Society built it’s 7-story headquarters near Wall Street, and which included two elevators.

The Value of a View?

How much of this premium is due to views, or increased social status, or more productive workers is still not fully understood; but what is clear is that people in big cities are willing to pay to be high in the sky. It’s also worth noting that this benefit also rests on our particular evolutionary history. Imagine that all humans had an innate fear of heights; that working in high-rise building automatically generated dread and anxiety? If so, the world would look radically different.

Elevator Dilemmas and their Remedies

The earliest elevators were driven by steam or hydraulics. And it was not until widespread use of electricity in the 1880s that efficient speeds were obtainable. Once this barrier was removed, however, a host of new problems arose. Faster speeds allow for taller buildings, which means more people, which generates more congestion and logistical problems in getting people to their final destinations. For example, there’s the problem of waiting times once you push the button in the lobby. Then there’s limits on how many people can fit in one cab. And when it is filled with passengers, it seems to stop on a million floors before you get to yours. Not to mention the fact it’s socially awkward to stand in a cramped box with 15 strangers.

The Pain Index

Keep in mind that, in theory, one can move people faster by creating more elevator shafts and this is certainly necessary for larger or taller buildings. But extra shafts are the bane of developers, since they eat up income-generating space. For the time being, we are going to hold the number of elevators constant and focus more on movement and speed. We will come back to the “shafts problem” in a future post.

The key challenge for efficient mobility is that of minimizing what has been referred to as the Pain Index—the total time to it takes from once you hit the button to when arrive at your final location. Evidently, however, it’s not clear what people hate more—waiting in the lobby for the elevator to arrive, stopping more inside the elevator, or getting into a crowded car.

Traffic Flow and Optimal Stopping

One of the key problems is that of peak usage times. For example, in offices at 8:30am, it seems every employee wants to get into the elevators at the same time. With the old-school call system, when multiple users push the call buttons at the same time, the elevators move to where they were called first. But when many buttons are pushed at the same time the system gets gummed up, increasing waiting time.

Computing technology and software programming has helped mitigate the problem of how to efficiently allocate car space during the day and based on different kinds of traffic patterns. Today, most modern elevator systems employ computer algorithms to minimize travel times, using what is called the Destination Dispatching System (DDS). In real-time, the system analyzes the input data–where the buttons where pushed–and makes a list of who to put in which cars and where the cars are to stop. If with conventional elevators waiting took over a minute, the DDS could reduce that time to half.

Elevator Waiting Times versus Traffic Intensity. The red line is waiting times for the traditional call-button method. The green line is the standard DDS system. The yellow line is a dispatch system created by KONE. Source: De Jong (2008).

Zoning and the Double Decker

For a given set of elevator shafts, the spaces can be used more rationally by the use of zoning and double decking. Zoning is the process of limiting specific elevators to operate only in predefined zones. One elevator can stop for local service, but another one say only goes from the lobby to the higher floors. Zones are normally kept to around 10-20 floors. This reduces the number of stops for the zoned cars and speeds up its return to the lobby. To allow for even higher heights, supertall buildings often have sky lobbies where an express elevator take you there and then you transfer to a separate elevator that operates only up high. For very tall buildings, another way to use the shaft space more efficiently is to have two elevators operate within the same shaft. One way to do this is to have one elevator car sit on top of another, creating the double decker. Odd-floor travelers enter the bottom car, while even-floor travelers enter the top car after walking up a ramp.

Cable Height

As buildings get taller, the amount of rope needed to connect the elevator car to the motor becomes longer and longer. This is a problem as conventional ropes, made of steel, can cease to be functional. In very tall buildings, nearly 70% of the elevator’s weight comes from the cable itself and when it gets too long it cannot support its own weight. Companies that manufacture elevator systems are thus in a race to develop new types of ropes that are both stronger and lighter.  With conventional ropes the highest that one elevator car can travel is 500 meters (1640 feet; about 140 floors). After that, going taller requires transferring to a new elevator at a sky lobby. The Jeddah Tower is going to install KONE’s “UltraRope,” which has a carbon-fiber core, making it particular light and strong. With this rope, cars can now travel up to 1000 meters (3280 feet), and it pushes possible skyscraper heights upwards (is this the egg for first mile-high tower?).

Human Physiology

Then there’s the problem of the human body, with its delicate carbon-based controllers and pain receptors. To quote James Fortune, a partner at FS2 Consulting, which specializes in elevator designs for supertall towers, “The human body has various internal sensors that are sensitive to external motion forces, noise, and vibrations. These sensors provide constant feedback to the brain and are quite responsive to any “out of the ordinary” elevator vibrations or noises.”

In particular, humans are quite sensitive to the acceleration and deceleration rates, which can cause ear discomfort due to the rapid changes in air pressure. Fortune says that, “However, ear comfort and pressure changes do not usually affect healthy elevator riders unless the descent speeds exceed 10 meters per second (m/s) and vertical travel exceeds 500 meters. For this reason, virtually all the latest supertall high-speed lifts, with “up” travel speeds to 10 to 20.5 m/s, have a maximum “down” speed of 10 m/s. Some cutting edge elevators, such as those installed at One WTC add extra air pressure on the way up to help prevent the annoying ear-popping sensation.

A History of Speed

While it’s fun to focus on the history of speeds, the truth is that the fastest elevators in the world are mostly used for visiting decks and/or to give bragging rights to the developers and companies that install them. For most office buildings, the average maximum speed is about 21 feet per second (5.8 m/s). Nonetheless, as the technology for speed and comfort progresses, it is likely that their benefits will be more widespread. In 1913, the world’s tallest skyscraper, the Woolworth Building, had a maximum speed of 11.6 feet per second (3.6 m/s). In 1931 the Empire State Building, had a maximum speed of 20 feet per second (6.1 m/s). So in in some sense, the top elevator speeds for the typical building haven’t changed all that much. What has changed is that passengers can be much more rapidly moved based on logistical algorithms, zoning, and double deckering. The efficient allocation of occupants is really what allows for buildings to go taller and taller.

The Record Breakers

Be that as it may, the figure below demonstrates the history of maximum elevator speeds over the last century. The left figure shows the speeds (feet per second) for the world’s record-breaking skyscrapers. (Note the Shanghai Tower is also added to the graphs. It did not have record-breaking height but did have record-breaking elevator speed).  This figure is clear: maximum elevator speeds have been rising over time. A back-of-the-envelope calculation shows that from the Singer (1908) to the Shanghai (2015), the maximum speed as increased at an average annual rate of 1.78% per year.

The right figure is speed versus the number of stories for the world’s record-breaking buildings. Again, we see a positive relationship. But, while the graph shows elevator speed versus height, we could be equally as justified in showing height versus speed, since we still can’t say which was the chicken and which the egg. All we can say is that the graph shows a strong correlation but says little about causality.  Another thing, however, pops out in this graph: the world’s fastest elevators are not in the world’s current record-breaker.

The Burj Khalifa’s elevators can move at a speed of 33 feet per second (10 m/s) and the Jeddah Tower, under construction, is expected to be the same. These are much slower than the Taipei 101 and the Shanghai Tower. In other words, what these findings suggest, again, is that speed, in and of itself, is not paramount. Likely the cost of operating super fast elevators and need to maintain passenger comfort and efficiency of movement currently trump speed.

The Evolution of Maximum Elevators Speeds over the Past Century. Left: Maximum elevator speeds for the world’s tallest buildings versus year of completion. The graph shows that speeds have been steadily increasing since the early 1900s. Right: Elevator speed versus building heights. Notice the world’s fastest elevators are currently in the Shanghai Tower, not the Burj Khalifa. Source: The Skyscraper Center.

The Future of Vertical Transportation

What’s in store for the future? Certainly, we can say that the big five manufactures–Otis, KONE, Thyssenkrupp, Schindler, and Mitsubishi–will continue to invest in R&D to push the elevator envelope, thus encouraging developers to build taller. But what revolutionary technology comes next? Who knows?  Likely futuristic buildings will have mag lev elevators with horizontal circulation. In 1957, Frank Lloyd Wright’s design for the one-mile high building called for nuclear powered elevators. But we’ll leave a discussion of these moon-shot technologies for the future, or rather, a future post.

Continue reading. The rest of the series on the technology of tall can be found here.

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Building the Skyline can be purchased through Amazon or Oxford University Press.

Credits

The New Amsterdam map on this page was sourced here, and the atlas image is from the 1891 Atlas of City of New York by GW Bromley & Co.

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