The PANEL Procedure

Between Estimators

The between-groups estimator is the regression of the cross section means of $\mb {y}$ on the cross section means of $\tilde{\mb {X}}_{s}$. In other words, you fit the following regression:

\[  \bar{\mi {y}}_\mi {i \cdot } = \bar{\mi {\mb {x}}}_\mi {i \cdot }{\beta }^{BG} + \eta _\mi {i}  \]

The between-time-periods estimator is the regression of the time means of $\mb {y} $ on the time means of $\tilde{\mb {X}}_{s}$. In other words, you fit the following regression:

\[  \bar{\mi {y}}_\mi {\cdot t} = \bar{\mi {\mb {x}}}_\mi {\cdot t}{\beta }^{BT} + \zeta _\mi {t}  \]

In either case, the error is assumed to be normally distributed with mean zero and a constant variance.