1 if treated, 0 otherwise
age of individual
years of schooling
1 if Black, 0 otherwise
1 if Hispanic, 0 otherwise
1 if married, 0 otherwise
1 if no degree, 0 otherwise
real earnings in 1974
real earnings in 1975
real earnings in 1978
1 if included in the Dehejia and Wahba (1999) sample, 0 otherwise
1 if included in the early RA sample of Smith and Todd (2005), 0 otherwise
0 if NSW, 1 if PSID, 2 if PSID-2, 3 if PSID-3, 4 if CPS, 5 if CPS-2, 6 if CPS-3
= re78-re75
= re74==0
= re75==0
= age^2
= (age^3)/1000
= educ^2
= re74^2
= re75^2
= black*u74
= educ*re74
= u74*hispanic
= married*re74
= married*u74