Confounding in Diff-in-Diff
Pr(X = 1 | A = 0)
Pr(X = 1 | A = 1)
Effect of A on Y^0
Time effect on Y^0 (t=1)
Time effect on Y^0 (t=2)
Effect of X on Y^0 at t = 1
Effect of X on Y^0 at t = 2