An Adversarial or "Long and Squiggly" Test of the Plausibility of Parallel Trends in Difference-in-Differences Analysis
An Adversarial or “Long and Squiggly” Test of the Plausibility of Parallel Trends in Difference-in-Differences Analysis Don’t worry, this is not a complicated post on yet another of the expanding set of theory papers on difference-in-differences. Instead, I want to offer my heuristic thoughts on when I find graphs illustrating parallel trends to be more or less informative, and on what, in my mind, makes the parallel trends assumption more plausible. If you take anything from this post, it should be: · · The longer and squigglier your pre-treatment trends, t...
Source: worldbank.org