在老王官网吗,一直碰到各种问题 加上变量 There exist time-invariant individual(s) (maybe only one obs): ,year must have multiple distinct nonmissing values
去掉不随时间而变化的变量后,一直出现如下xtdev2(): 3301 subscript invalid
thestm2(): - function returned error
<istmt>: - function returned error