Sunday, January 31, 2016

When You Have Multiple Measures of the Same Thing...

The usual problem when doing empirical work is that you don't have an important variable in your data. Very, very occasionally, you have the opposite problem: Lots of different highly correlated variables measuring pretty much the same thing. What to do? How to choose?

I would say that if the variable is typically measured in a specific way in the (economics) literature, maybe go with that one for your main specification unless you have reason to believe you have a better one. Either way, include a table in the appendix showing that your results are robust across measures. Don't freak out if you fail to see a star for one or two of them. This will happen if you have enough different measures and not a large enough sample size.

Another good option to choosing just one for your main specification is to include a summary measure of all of the different measures. Of course, many ways to create summary measures. Have a look here for a nice discussion of this.

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