I am using data from a controlled experiment with different timing of treatment implementation across individuals in the treated group. I can date treated observations with time distance to the implementation dates; However, how can I make a trend plot for control group? In particular, how to date the trend for control individuals?
I found that the good way to do it is using "stacked cohort" diff-in-diff, where you create a dataset that covers a time window for each event, and then stack up the datasets into one. One example is in Gormley and Matsa (2011).