如题,分组回归的样本数加起来大于总的不分组回归的样本数,请问是什么原因造成的呢?找了好久原因没想明白。代码如下:
总体回归:xtreg ROA L.donationrate22 lnsize top1 advert debt age type L.do EU doEU i.year,fe r
分组回归:
xtreg ROA L.donationrate22 lnsize top1 advert debt age type L.do EU doEU i.year if lifecycle==1 ,fe r
xtreg ROA L.donationrate22 lnsize top1 advert debt age type L.do EU doEU i.year if lifecycle==2 ,fe r
xtreg ROA L.donationrate22 lnsize top1 advert debt age type L.do EU doEU i.year if lifecycle==3 ,fe r


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