Monday, 7 November 2016

East Side Story: Historical Pollution and Neighbourhood Sorting

The East Sides of cities such as London, Vancouver, New York and Paris have historically been the poorest. Some, but not all, have gentrified more recently, and this gentrification has been at the centre of media attention. These observations uncover two questions. Why were these neighbourhoods poor to begin with, and why did some gentrify while others did not? Research conducted by Stephan Heblich (University of Bristol), Alex Trew of the School of Economics & Finance (University of St Andrews) and Yanos Zylberberg (University of Bristol) ( suggests that this observation is the most visible consequence of the historically unequal distribution of air pollutants across neighborhoods. During the Industrial Revolution, many areas of Manchester, for example, were covered with layers of soot. Black stains on the pavements and buildings of areas such as Victoria Station or Ancoats in North-East Manchester remained until very recently. With the wrong weather, some areas could be submerged under dark, thick smog. This environmental disamenity made them unpleasant places to live and, in response, those who could afford moved to the neighbourhoods spared by the pollution. This sorting resulted in an unequal distribution of social classes across the city. Since the prevailing winds (The Westerlies) in London, Vancouver, New York, Paris or Manchester blow from the West to the East, the most visible component of such process ended up being the observed West-East differential in neighbourhood composition.

The authors examined nearly 5,000 industrial chimneys in 70 English cities in 1880 and use an atmospheric dispersion model to recreate the spatial distribution of pollution. The exercise was possible because of the fastidiousness of Victorian cartographers. These pioneering map-makers marked each building with landmarks such as factory chimneys. In addition, Victorian census-takers conducted detailed population studies over the nineteenth century.

There is a strong connection between the presence of air pollution and the share of low-skilled workers at the end of the nineteenth century. Such a correlation was absent before coal became the major energy source at the beginning of the century. The observed effect is substantial: the difference between being in the 10% and 90% most polluted neighbourhoods of Manchester was a difference of about 20 percentage points in the share of low-skilled workers. Most interestingly, the relationship between the presence of historic pollution and the share of low skilled workers in 2011 turns out to be quantitatively comparable to the one observed at the end of the nineteenth century. The previous result leaves one question unanswered. How could sorting caused by 1880 pollution be visible nowadays almost 100 years after the 1926 Smoke Abatement Act and 50 years after the Clean Air Acts (which quickly and considerably reduced the extent of coal-based pollution within cities)?

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