不知道是不是回归的命令不对,所以我把命令也发过来。其中,wtangibility是工具变量,cashnew是自变量,wzcash是因变量。
xi: xtreg cashnew  wtangibility wsize1 wleverage1 wleverage2 wsellingcostnew1 wsellingcostnew2  wlabornew1 wlabornew2 winvestment1 winvestment2  wmktgrowthnew1 wmktgrowthnew2 i.IDdm, fe i (year)
predict  cashnew_2, xb
xi: xtreg wzcash cashnew_2 wsize1 wleverage1 wleverage2 wsellingcostnew1 wsellingcostnew2  wlabornew1 wlabornew2 winvestment1 winvestment2  wmktgrowthnew1 wmktgrowthnew2 i.IDdm, fe i (year)