In the 1920s and 30s, scholars at the Chicago School of urbanism came up with a standard model, in which the city was a series of concentric circles. At its centre, they placed factories and employment centres; these were surrounded by working class housing. Then came the middle classes, and finally, at the city’s edges, those with the highest incomes.

Anyone who’s visited the US recently can tell you this model no longer holds (there’s a real scarcity of factories in Times Square these days). But a study released by the Martin Prosperity Institute in September goes further: now, it argues, this model has now been completely inverted.

A team of researchers, including urbanist Richard Florida and cartographer Zara Matheson, used 2010 census and survey data to map the class breakdown of 12 major US cities. Unlike the Chicago School team, however, they didn’t classify people by wealth, but by three classes of employment: the confusingly named “creative class”, which includes professional jobs like lawyers or doctors; the “service class”; and the “working class”, meaning manufacturing or factory workers.

The study found that the creatives increasingly dominate the centre of most cities; where there’s a waterfront, they also cluster there. Meanwhile, those with service jobs tend to live further out. True working class neighbourhoods are now a relative rarity.

The economic centre of New York, for example, is Manhattan. The island is now almost exclusively occupied by the creative and professional class, except for a few service-dominated areas in Harlem or on the Lower East Side. The outer boroughs are dominated by the service class, while only a handful of areas in Queens and the Bronx are even 50 per cent working class these days:

The study doesn’t include comparative historical maps, but just about every film ever set in New York tells you that this wasn’t always true. In the 20th century, Manhattan was dominated by recent migrants living in tenements. This “creative class” concentration is a recent phenomenon, a result of the city’s shift away from an industrial economy.

Other post-industrial metros like Boston show a similar pattern, though there are a few service workers still living in the south-central part of the city:

The outer edges of Houston are still dotted with petrochemical and aerospace factories. Consequently, the city still has a few working class neighbourhoods on its outskirts:

Is any of this a problem? The study concludes that it has identified “clear and unmistakeable patterns of class division”, which doesn’t sound great. But the Chicago School model suggests that this has probably always been the case.

What has changed is where people want to live, given the choice. With the disappearance of heavy industry and the accompanying noise and pollution, city centres are now more attractive to wealthier residents. And, as industry moves elsewhere, the number of blue-collar jobs in cities is falling.

It might be those brown and beige clumps representing the service class, almost always slightly outside the economic centre, which we should be worrying about. The study identifies what it calls “areas of urban disadvantage”: suburbs populated by those who may well work in service jobs in the city centre, but can only afford to live at its fringes. An income map of New York effectively mirrors the job-based map above:

In other words, the Martin Prosperity Institute maps are about income after all. As richer people move in, property prices go up – and it gets harder and harder for those who aren’t wealthy to live near city centre.

First three maps: Richard Florida/Martin Prosperity Institute; final map: US Census.