use ${temploc}junk,clear
mac def sort="$family `*'"



/* sorts data in ram by $sort & within by group defined by $sort,
	counts the number of year 1 & year 2 observations.
	$y1 is the count of year 1 observations & $y2 is the year 2 count. */

sort $sort year
mac def y1 : tempvar
mac def y2 : tempvar
qui by $sort : gen byte $y1=year==$yr1
qui by $sort : replace $y1=sum($y1)
qui by $sort : replace $y1=$y1[_N]
qui by $sort : gen byte $y2=year==$yr2
qui by $sort : replace $y2=sum($y2)
qui by $sort : replace $y2=$y2[_N]

save ${temploc}junk,replace
keep if $y1==1 & $y2==1
if _N>0 {
	drop $y1 $y2
	replace match_id=year==$yr1
	replace match_id=sum(match_id)
	replace match_id=match_id + $leftoff
	mac def leftoff=match_id[_N]
	replace level=$step*2 - 1
	if $step==1 {
		save ${temploc}matched,replace
	}	
	else {
		save ${temploc}_temp,replace
		use ${temploc}matched
		append using ${temploc}_temp
		save ${temploc}matched,replace
	}
}
use ${temploc}junk,clear
drop if $y1==1 & $y2==1
save ${temploc}junk,replace
exit 0