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Insulting QR?

Nathan Grawe
published May 2, 2014

This recent study by McDermott, Fowler, and Christakis has gotten a little news coverage recently. The authors conclude that divorce is contagious. They find that the probability of divorce increases 75% when someone in your social network gets a divorce of their own. Even if someone once removed in your network (a friend of a friend, for example) gets divorced your odds of divorce go up 33%.

What I found most curious was this review in Psychology Today. The reviewer doesn't like the conclusions in McDermott et al. "There are covert but powerful social norms and expectations, however, there is simply too much information missing in this research for me to conclude that divorce is contagious. I think this statement insults the integrity of every person who finds themselves facing this incredibly difficult choice.... I hope the readers of these articles can see past the surface level findings. Divorce is not contagious. Divorce is not an epidemic and it is not a disease that is transmitted."

Like the reviewer, I was initially skeptical of the study. After all, there are many factors that determine divorce and so it is prudent to ask, "Controlling for what?" Reading the study, there is some reason for concern. The primary control variables are age and education. However, it's a neat data set. (Read the "Sample" section of the paper linked above.) One neat aspect is that they can distinguish between person A viewing person B as a relation vs. person B viewing person A as a relation. This permits the authors to estimate separate effects depending on the direction of the relationship. As the authors explain, if a confounding relationship explains the effect then it shouldn't matter which way the relationship flows. Yet, they find a strong "contagion" effect when the divorcee is viewed as a relation. When the relationship only runs the other way, the effect size is cut to one-third and is no longer statistically significant.

While I am not ready to declare the "law of divorce contagion," the above seems like evidence I have to deal with. To dismiss definitely careful scientific research just because we don't like the results limits our potential to learn new things. And presumably that's why we are doing the research, right?

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