Building the Skyline: The Birth and Growth of Manhattan’s Skyscrapers.By Jason Barr.Oxford University Press; 437 pages; $49.95.

THE world is in the middle of an unprecedented skyscraper boom. Last year more than 100 buildings over 200 metres tall were built. What forces drive such ambition? A new book by Jason Barr, an economist at Rutgers University-Newark, focuses on Manhattan, and shows why these behemoths develop, in a conversational style that almost makes you forget that you are reading a book about economic history.

Why is Manhattan synonymous with skyscrapers? In the late 19th century the island was booming: demand to be in particular areas was so high that the only option was to build up. But geography also played a role. The famous grid pattern of the city’s streets, imposed early in that century, meant that the average plot of land in the city was fairly small. Manhattan is itself a thin piece of land, making it hard for economic activity to spread out, Mr Barr notes.

New York’s first skyscraper, the 11-storey Tower Building, went up in the 1880s. Situated on Broadway, it was a technological breakthrough. The architect, Bradford Lee Gilbert, realised that supporting a super-tall building using conventional techniques would require walls so thick that there would be little floorspace left. So he created an iron frame for the building (after which the only function of the walls was to keep the rain out). On a gusty morning in 1888, New Yorkers anxiously watched Gilbert as he climbed right to the top.

Along the way, Mr Barr punctures some skyscraper myths. For instance, there are relatively few towers between Downtown and Midtown. Urban folklore has it that New York’s geology is the reason: the bedrock in that part of town, the assumption goes, cannot support tall buildings.

A better explanation is New York’s economic history. Mr Barr argues that the area between Downtown and Midtown historically had low land values. In the 18th century the rich lived in Downtown areas close to the port and the seat of government. The poor lived just outside. The wealthy reacted to the gradual introduction of public transport in the 1820s and 1830s by moving far out, eventually as far as Midtown, a less-developed area which could be built to their tastes. The in-between zones thus left behind were undesirable, and few people thought it profitable to build skyscrapers there. The spatial economics of the 19th century continues to shape Manhattan’s skyline today.

Mr Barr tackles another popular myth, often referred to as the “skyscraper curse”. Some economists reckon that a boom in skyscraper construction artificially forces up the price of land; developers want to build an even taller building than their rivals, so they furiously compete for plots. This can push an economy into bubble territory, the thinking goes. Indeed, the 1920s was a period of frantic floor-adding, often with little economic rationale. It culminated in the opening of the Empire State Building in 1931—just as the Great Depression bit. However, Mr Barr’s careful statistical analysis indicates that over the long sweep of history, skyscraper construction is rational: bursts of activity tend to follow an increase in land values, but not the other way round.

Economists will appreciate Mr Barr’s careful use of wonky concepts; architects and historians will enjoy his keen eye for detail. But whatever your persuasion, after reading this book you will never look up at a skyscraper the same way again.