Monday, March 1, 2010

Brief: Trust and crime

I've been thinking more about trust and its effects on all areas of social interaction and culture. It's at the root, really: if you don't trust others, you will try to get by on your own. Sociability requires a certain level of trust, and in a social species like ours there are gains to be had by interacting with others -- especially in a modern market economy where you can outsource so many things to others in the market instead of doing them yourself. You don't make your own shoes, grow your own food, manufacture your own computer, or gather your own news about the President. Sounds great -- why would you possibly withdraw from that sociability?

If you trust others, you're making yourself vulnerable to exploitation. The more trusting people there are in a population, the easier it will be for exploiters to thrive, and that will drive up their numbers. The exploiters may become so numerous, and their effects so offensive, that people start to withhold their trust lest they become the next statistic. That state-of-mind could show up in behavior by simply not venturing out into the public sphere where they'd be vulnerable, hiding out in the safer personal sphere.

But then when there are far fewer trusting people, that dries up the resource that exploiters had been thriving on. Now there are lots of them competing to exploit a shrinking number of trusting people. So that will drive down the numbers of exploiters. Eventually people will realize how safe things have become and extend their trust once again, which will in turn drive up the numbers of exploiters as before, and the cycle repeats.

This variant on a model of how hosts and parasites, or predators and prey, interact in ecology suggests looking at data on how trusting people have been over time, and what the crime rate has been like. Before I showed that people rationally respond to changes in the homicide rate by becoming more afraid when it's going up and less afraid when it declines, with about a 2-year lag. So we know that perceptions are affected by crime levels -- but could crime levels be affected by perceptions, i.e. how trustworthy you think other people are?

The General Social Survey asks respondents whether other people can be trusted, cannot be trusted, or that it depends. Here is a plot over time of the percent of respondents who said that other people can be trusted (in black), together with the homicide rate (in red):

Clearly the relationship is less stark than it was for fear resonding to crime, where the correlation within a year was +0.74. Still, the correlation here is +0.53, meaning that indeed higher crime rates are associated with higher levels of trust. And as in the case of fear and crime, that understates the strength of the relationship since there is a time lag. In particular, trust levels started falling steadily before the homicide rate did so. So the predicted relationship is there: crime rates are high throughout the '70s and '80s, and at some point in the mid-late-'80s, people have had enough and start trusting others less and less. With far fewer trusting people to exploit, criminals start scaling back or dying off: the homicide rate peaks in 1991 and starts falling steadily afterward.

We will have to wait a few more decades to see if the rest of the story pans out -- whether with such low crime rates, people will assume it's safe to start trusting people again, and whether those higher levels of trust (if they did happen) would be followed by a rise in the crime rate.

Criminologists and others debate what causes crime to go up or down -- tougher or more lenient punishment by the government, technology that makes it easier or harder to report crimes, etc. I have only a passing familiarity with the range of causes they discuss, but as far as I know, how trusting the average person is does not get much attention, although there may be some minority contingent that does look at it. Perhaps it is as simple as a rise in crime following an increase in the number of people who criminals would consider "suckers," and a decline in crime following a contraction in the numbers of "suckers," just as we see between a host species and a parasite species. The logic is hard to argue against, and the graph above shows that it has some modest empirical support as well.

GSS variables used: trust, year

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