Tools · Interactive

Difference-in-Differences Visualizer

See how a violation of parallel trends poisons the naive estimate — and how DiD recovers the truth.

Interactive · Figure Difference-in-Differences: in motion Drag the sliders to see how a violation of the parallel-trends assumption poisons the naive estimator.

True treatment effect+15 Pre-trend divergence (violation)0

Naive post-comparison +0.0 Treated − Control at the end

DiD estimate +0.0 Removes any common trend

Bias (naive − true) +0.0 What you would over-claim