clear 

use ds1, clear 
gen byte firstyear = .

mata:
names = "s72 s73 s74 s75 s76 s77 s78 s79 s80 s81 s82 s83 s84 s85 s86 s87 s88 s89 s90 s91 s92 s93 s94 s95 s96 s97 s98 s99"
st_view(s=., ., tokens(names))
st_view(first=., ., "firstyear")

for (i=1; i<=rows(s); i++) {
	for (j=1; j<=cols(s); j++) {
		if (s[i,j]==1) {
			first[i] = j+71
			break
		}
	}
}
end