Political map of London is like America: strong geographic segregation

Thomas Schelling is a brilliant American polymath, who deservedly won the Nobel Prize in economics in 2005.  One of his most remarkable insights is about segregation in cities, which he published as long ago as 1971.

The residential pattern of American cities tends to be pretty sharply divided on ethnic grounds.  The population of many areas is often overwhelmingly drawn from a single ethnic group.  There are white neighbourhoods, black neighbourhoods, as so forth, in which there are very few members of other ethnic groups.

An obvious implication of this seems to be that there is strong racial prejudice in the US, that many people actively prefer to live amongst people of their own ethnicity.

Schelling showed that strong segregation at the level of the city as a whole can arise even when individuals have only a very weak preference in favour of being surrounded by people of their own ethnic group.  There is a big, often highly mathematical, scientific literature on this in the four decades since Schelling made his discovery.  But his basic finding still remains valid.  Very weak individual preferences often translate into apparently very strong ones at the city-wide level.

His work was all the more remarkable given that personal computers had not been invented. Schelling obtained his results using coins on graph paper.  He placed pennies and nickels in different patterns on the "board" and then moving them one by one if they were in an "unhappy" situation.

Source: Guardian newspaper


The first preferences in the 2012 London Mayoral election are a remarkable example of city-wide segregation. They give the impression of a city which is sharply divided in its political allegiances and outlook.

Of course, many factors determine electoral outcomes. And the chart is not implying that people select their place of residence according to its political preferences. But, certainly, there is a self-reinforcing aspect to this process, which Schelling did not incorporate into his original model. The underlying maths of these models came much later.

The overall culture of a locality is an important determinant of an individual’s political preference. Many wealthy left-wingers, for example, choose to live in the Labour areas immediately north of the river in the centre of the city. They do so because of the local culture, which in turn reinforces their own opinions and voting habits. So we have a Schelling-type process underpinning the electoral map, overlaid with the kind of self-reinforcing feedbacks which pervade modern life.

A very American outcome in Europe’s leading city!