*! version 1  22Nov2000 by Duolao Wang   (STB-59: sbe42)
* hernes -- a command that fits the Hernes (ASR 1972) model of
* proportion of a cohort every-married by age.
* The command takes two arguments: "age" for age in years and
* "rate" observed age-specific cumulative proportions married

program define nlhernes
	version 6
	if "`1'" == "?" {
		global S_1 "a b k"
		global a=$a0
		global b=$b0
		global k=$k0
		exit
	}
	replace `1'=1/(1+1/($k*$a^($b^(t))))
end