There is a vast amount of literature that links the location (or density) of alcohol outlets with crime, particularly violent crime. I've contributed to this literature on a number of occasions (see here and here and here, for example). However, one criticism of this literature is that, while it shows that the number or density of alcohol outlets and crime are correlated, it doesn't demonstrate causal relationships between alcohol outlets and crime. These studies are all based on what are termed ecological relationships. We see more outlets where there are more crimes, and we infer that the outlets cause the crimes. There are good theoretical reasons to believe this relationship is causal, but the statistical tools that are used don't demonstrate this definitively.
The relationship between alcohol outlets and crime is something I've been working on during my current study leave period, which is due to finish soon. I'll be presenting some causal analysis (based on instrumental variables regression) at the New Zealand Association of Economists Conference at the end of this month. However, that isn't the only important work I've done in this space over the last year.
One of the key criticisms of the ecological literature on alcohol outlets and crime is that the spatial pattern of alcohol outlets is essentially the same as the spatial pattern of retail activities more generally. Alcohol outlets tend to locate in the same places that retail outlets of all types tend to locate. So, any observed relationship between alcohol outlets and crime might not be due to the alcohol outlets themselves, but rather due to retail outlets generally. This criticism can be backed up by a theory in criminology known as routine activity theory. Routine activity theory says that crime occurs when there is a motivated offender and a potential target that are in the same place at the same time, in the absence of a capable guardian (that is, someone who can prevent the crime either directly or indirectly). It can be argued that areas where there are retail activities are mostly deserted at night, reducing the number of effective guardians, and therefore making crime more likely.
Some years ago, I had a couple of summer research students look into the relationship between a range of different retail outlets and violent crime in Hamilton. I recently followed that up with some more thorough and detailed analysis, and the results of that have just been published in the influential journal Addiction (sorry, there is no ungated version online). I used data on the number of alcohol outlets (by type) from the Ministry of Justice, data on the number of non-alcohol outlets (by type, separately for licensed clubs (like sports clubs), bars and night clubs, other on-licensed outlets (like restaurants and cafes), and all off-licence outlets (including bottle stores and supermarkets)), and data on violent crime calls-for-service and total calls-for-service from the New Zealand Police, all measured at the area unit level (approximately suburb level) for Hamilton. The non-alcohol outlets data were painstakingly collected by my research students, by visiting every commercially-zoned area in Hamilton and observing the types of outlets located there. They collated data on the number of bakeries, hairdressers, service stations, and takeaway food outlets, for each commercial block, which we then aggregated up to the area unit level.
My analysis was conducted in a couple of steps. First, I find that the number of outlets of each type (separately for each type of alcohol outlet and for each type of non-alcohol outlet) are highly correlated with each other. That suggests that it would be difficult to disentangle the effects of alcohol outlets from the effects of retail more generally, as expected. This demonstrates the problem that a lot of the literature faces.
Second, I use the data on the non-alcohol outlets to create a measure of retail density for each area unit, and show that, after controlling for non-alcohol retail density (as well as population, local demographics, and social deprivation), statistically significant semi-partial correlations remain for each alcohol outlet type and both violence and total calls-for-service. That tells us that the relationship between alcohol outlets and crime is not purely an artefact of retail density, since alcohol outlets can explain some of the remaining variation in crime even after retail density is accounted for.
The contribution of this paper seems small, but it is likely to be important. While this research doesn't quite get us to a demonstration that alcohol outlets cause crime, it does at least eliminate one of the common counter-arguments against the literature. Now we need to follow this up by applying alternative methods to demonstrate causality, and that is what I am working towards. Watch this space.
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