Coral__ 发表于 2021-3-12 16:02 
楼主解决这个问题了嘛??我也想问如果最终所有样本都受到了冲击,那么什么是对照组呢?
看了一篇文章 《The Impact of Venture Capital Monitoring》 Bernstein等(2016) 可以看下 尤其这句话所处段落 To account for this possibility, we use a control group that consists of all VC-portfolio company pairs that have not been treated by 1988.