## FANDOM

15 Pages

Requires strict exogeneity $E[u_{it}|x_{i},c_{i}]=0 \, t=1,...T$. Intuitively, this is because every $y_{it}, x_{it}$ needs to be demeaned (the within transformation) - since the mean depends on past, current and future values, we need that $u_{it}$ is uncorrelated with all $t$.

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