A beginner-friendly tour of seven panel-data estimators — POLS, Between, First-Differences, Fixed Effects, Two-Way FE, Random Effects, and Correlated Random Effects (Mundlak) — applied to a two-period worker wage panel.
Manual demeaning vs two-way fixed effects --- showing that TWFE is just OLS on demeaned data through the Frisch-Waugh-Lovell theorem, with a hands-on proof using a Barro convergence panel of 150 countries.