Difference-in-differences compares outcome changes across exposed and unexposed groups. Its standard identifying condition is that their untreated outcomes would have followed parallel trends.
Articles by others on the same topic
Difference in Differences (DiD) is a statistical technique used in econometrics and social sciences for estimating causal effects. It is particularly useful in observational studies where random assignment to treatment and control groups is not possible. The method compares the changes in outcomes over time between a treatment group (which receives an intervention) and a control group (which does not).