Triple differences Part 1
Triple differences is greater than the sum of its two diff-in-diff parts
Gruber’s 1994 triple differences paper
The year 1994 is a special year for me both for sentimental and nerd reasons. It was the year I graduated from high school and the year I started college at the University of Tennessee Knoxville. The best of times and the worst of times, let’s just say. But it was also the year that Card and Krueger published their famous New Jersey and Pennsylvania article on the minimum wage which used difference-in-differences. They published that paper in the number 4, volume 4, September issue of the American Economic Review. While that paper wasn’t the first paper to use diff-in-diff — it had been used by Orley Ashenfelter and David Card many years earlier — it was nonetheless a paper that put a spotlight on diff-in-diff because the empirical application (the minimum wage increase in a low wage industry) was so well designed and yet found no evidence of disemployment effects. Difference-in-differences after that paper appeared to begin its ascent in the…
Keep reading with a 7-day free trial
Subscribe to Scott's Substack to keep reading this post and get 7 days of free access to the full post archives.