找到一段英文是这样描述的:Table 4 reports the estimates of Eq 4 aggregated over the years. The firstcolumn presents the averages of the annual coefficient estimates, and thesecond column presents an aggregate z-statistic, calculated as the sum ofindividual annual z-statistics divided by the square root of the number ofyears.
按照这个步骤可以一步步算出来,想问下stata有没有简单的命令,可以直接求出来的。谢谢