One of the beautiful things about economic research is that you can ask questions like, "Where does crime come from?" and, rather than boring stock answers like "bad people," you can uncover deeply fascinating ones -- like "the weather."

There's established literature documenting changes in climate or rainfall and changes in crime rates. In a review of previous research, Harvard Business School professor Lakshmi Iyer and International Monetary Fund economist Petia B. Topalova explain that, from 10,000 BCE all the way to today, 

Deviations from normal in precipitation and air temperature raise the likelihood of violent crimes (such as murders), intergroup conflict (such as riots and rebellions), political violence, civil war onset, and even institutional breakdowns. 

Why does this happen? There is some evidence that higher temperatures make people angrier, and of course, there could be a direct link between things like heavy rain and the movement of troops.

But what if weather affected something that we can do something about, like poverty? 

How weather affects crime 
In a Harvard Business School working paper, our fearless researchers set to work tackling the issue. 

Looking at decades of data from India, Iyer and Topalova confirm that drops in rainfall (pun absolutely intended) affect both poverty and crime. More rain is correlated with higher consumption and a fall in the poverty gap, and less rainfall with lower consumption and higher poverty. It also affects criminal behavior: a sudden reduction in rainfall leads to more violent crime and property crimes.

It's kind of weird: More rain seems to equal less crime.

But how do you know if it's poverty or just bad temper? Iyer and Topalova compare rainfall effects to another major change in India: the loosening of protectionist trade policies, which affected different regions at different rates, and in different ways. Here they also find a close link -- higher tariffs appear to correlate with lower crime rates (mostly violent crime, property crimes, and economic crimes).

The difference is that rainfall affects pretty much everyone, while the trade policy changes studied mostly affect the poor. And that's exactly what the researchers found: Average consumption and crime are closely linked when it comes to rainfall, but poverty and crime are more connected when trade policies change.

In both cases, more poverty correlates with more crime. 

This is actually good news
Dinner party conversation aside, the fact that economic factors affect crime rates is actually good news: As a society, we can do something to help people offset economic loss. 

Iyer and Topalova found that a social welfare policy in India hasn't worked as intended in reducing the economic consequences of drought, even though it has had positive repercussions in other areas. With this knowledge, the policy can be studied further, and perhaps reimagined to better serve the people it's supposed to help. Future policies could all be viewed through the lens of economics and crime; after all, criminal activity affects everyone.

In the end, we can't change the weather, and we sometimes choose the "greater economic good" over the interests of a few -- but that doesn't mean there aren't consequences, and it doesn't mean we can't do anything about them. 

Once again, the beauty of economic research. 

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