My experience with blogging tells me that a post on applied econometrics is always a good way to start the week by generating a large number of views, so let me do a ‘Metrics Monday yet again this week.
A few weeks ago, Google Scholar alerted me that a new working paper by Giuseppe de Luca, Jan Magnus, and Franco Peracchi might be of interest to me, given the research topics associated with my profile. (I was under the impression that their paper was forthcoming in the Journal of Labor Economics, but I somehow cannot find any evidence that this is so. No matter, this is an important contribution.)
Let me first present the abstract of the article, which even after reading three times, I had a hard time making heads or tails of given how cryptic it was. Then, I will present the first few paragraphs of the article, which illustrate the point much better. I’ll then go into the results, which are actually pretty important for applied econometrics.
Here is de Luca et al.’s abstract:
This paper studies what happens when we move from a short regression to a long regression (or vice versa), when the long regression is shorter than the data-generation process. In the special case where the long regression equals the data-generation process, the least-squares estimators have smaller bias (in fact zero bias) but larger variances in the long regression than in the short regression. But if the long regression is also misspecified, the bias may not be smaller. We provide bias and mean squared error comparisons and study the dependence of the differences on the misspecification parameter.
Somewhat cryptic, at least to my applied mind. The first two paragraphs of the introduction provide a better idea of what’s going on: