# Difference In Differences Analysis

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Compare change in place A with a change vs no change in place B - before and after. 

Requires a control group.

City A has taxes change, City B has no tax change. 

Want to figure out what vaariables were impacted by tax change in City A.

City B is control group. 

![illustration of isolation tax change-before](https://i.imgur.com/bmLTsM8.png)

![Illustration of isolation tax change-after](https://i.imgur.com/sS4Gr6H.png)