paneldata数据分析 一(7)

自变量因变量采取年度均值进行回归
④The number of observations is N. The time variation is not considered and the data are collapsed with one observation per inp>
⑤This estimator is seldom used because the pooled and RE estimators are more efficient。
缺点：低效。
组内估计或固定效应估计（Within estimator or fixed effects estimator）
①The within estimator uses the within variation (over time).
②It uses time-demeaned variables (the inp>
time-averaged values).比如说If an inp>
③This is an OLS estimation of the time-demeaned dependent variable on the time-demeaned regressors.

time-demeaned OLS regression