I was in Washington last month to discuss my work on food prices, in which I look at whether food prices cause social unrest, at an event whose goal was to discuss the link between climate change and conflict.
As many readers of this blog know, disentangling causal relationships from mere correlations is the goal of modern science, social or otherwise, and though it is easy to test whether two variables x and y are correlated, it is much more difficult to determine whether x causes y.
So while it is easy to test whether increases in the level of food prices are correlated with episodes of social unrest, it is much more difficult to determine whether food prices cause social unrest.
In my work, I try to do so by conditioning food prices on natural disasters. To make a long story short, if you believe that natural disasters only affect social unrest through food prices, this ensures that if there is a relationship between food prices and social unrest, that relationship is cleaned out of whatever variation which is not purely due to the relationship flowing from food prices to social unrest. In other words, this ensures that the estimated relationship between the two variables is causal. This technique is known as instrumental variables estimation.
Identifying Causal Relationships vs. Ruling Out All Other Causes
As with almost any other discussion of a social-scientific issue nowadays, the issue of causality came up during one of the discussions we had at that event in Washington. It was at that point that someone implied that it did not make sense to talk of causality by bringing up the following analogy: Continue reading →


9
Feb 12
On the (Mis)Use of Regression Analysis: Country Music and Suicide
This article assesses the link between country music and metropolitan suicide rates. Country music is hypothesized to nurture a suicidal mood through its concerns with problems common in the suicidal population, such as marital discord, alcohol abuse, and alienation from work. The results of a multiple regression analysis of 49 metropolitan areas show that the greater the airtime devoted to country music, the greater the white suicide rate. The effect is independent of divorce, southernness, poverty, and gun availability. The existence of a country music subculture is thought to reinforce the link between country music and suicide. Our model explains 51 percent of the variance in urban white suicide rates.
That’s the abstract of an article published in Social Forces – a top-10 journal in sociology — in 1992.
Before my snark gets me into trouble: Yes, I do realize that the article was published in 1992, back when most social science researchers only had a flimsy grasp of identification and causality. I also realize it would be foolish to impose on the authors of the above-referenced article the same standards of identification we impose upon ourselves today.
Yet, I cannot help but think that someone with a lesser of understanding of causality than the average reader of this blog is bound to eventually stumble upon the abstract, think “Hey, that totally makes sense!,” and run with it.
I’m sure there are also examples of such findings in other disciplines. If you know of any, please share.
(HT: Friend and former student Norma Padron, who is doing her PhD at Yale and has just launched a nice health economics blog.)