Wednesday 5 August 2009

Community Cohesion

CLG has been talking about the economic benefits of community cohesion. It is suggested that new figures show that increasing cohesion by 1 per cent across the country can potentially save up to £530m in reduced crime.

This figure is arrived at by pulling together two numbers. One is on the costs of crime (I haven't looked at this in detail). The other is on the correlation between crime and some measures of cohesion. The correlation comes from data on 20 areas (effectively 40 wards out of England's approximately 8,000). Crucial assumption number one is therefore that these areas are representative. A 0.5% sample is unlikely to achieve this. That aside, the crucial thing is whether or not these numbers capture a causal relationship from cohesion to crime.

Concluding that the relationship was causal would require us to rule out the possibility that the correlation was not just picking up some other characteristics of neighbourhoods that are correlated with both crime and measured cohesion (say, for example, the income level of the neighbourhood). At the very least, we would want to rule out some of the more obvious possibilities. Unfortunately, the original research didn't do this so we have no way of knowing what causes this relationship. Research that is more careful suggests that it is very difficult to attribute any differences in outcomes that we care about to the causal impact of these kind of community variables.

Cohesion is a bit like motherhood and apple pie. What reasonable person could be against it? Spending public money to achieve it may well be a good thing. But, whatever the claim, this research doesn't help improve our understanding of the wider economic benefits of doing so.