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use http://fmwww.bc.edu/ec-p/data/hayashi/griliches76.dta
xi i.year

ivreg2 lw expr s (iq=age kww med)

ivreg2 lw expr s (iq=age kww med) _Iyear_67 _Iyear_68 _Iyear_69 _Iyear_70 _Iyear_71 _Iyear_73

ivreg2 lw expr s (iq=age kww med) _Iyear_67 _Iyear_68 _Iyear_69 _Iyear_70 _Iyear_71 _Iyear_73, robust

ivreg2 lw expr s (iq=age kww med) _Iyear_67 _Iyear_68 _Iyear_69 _Iyear_70 _Iyear_71 _Iyear_73, gmm

ivreg2 lw expr s (iq=age kww med) _Iyear_67 _Iyear_68 _Iyear_69 _Iyear_70 _Iyear_71 _Iyear_73, gmm orthog(s)

ivreg2 lw expr (iq s=age kww med) _Iyear_67 _Iyear_68 _Iyear_69 _Iyear_70 _Iyear_71 _Iyear_73, gmm

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