drop _all
set obs 1
mac def dummy : tempvar
gen byte $dummy=1
save ${temploc}dummy,replace

use ${temploc}junk,clear
keep if $y1>0 & $y2>0 & ($y1>1 | $y2>1)
if _N==0 {
	use ${temploc}junk,clear
	drop $y1 $y2
	save ${temploc}junk,replace
	exit
}
sort $sort year
mac def guy : tempvar
mac def guy1: tempvar
mac def guy2: tempvar
mac def group : tempvar
qui by $sort year:gen byte $guy=_n
qui by $sort:gen int $group=_n==1
replace $group=sum($group)
save ${temploc}_junk,replace
keep $sort $group
qui by $sort:keep if _n==1
keep $group
save ${temploc}_reflist,replace
mac def HH=_N


capture prog drop doit
prog def doit

mac def hold "`*'"
mac def hh 1
while $hh<=$HH {
	use ${temploc}_reflist,clear
	keep if _n==$hh
	sort $group
	save ${temploc}__ref,replace
	use ${temploc}_junk
	sort $group
	merge $group using ${temploc}__ref
	keep if _merge==3
	drop _merge
	sort $group
	save ${temploc}_fam,replace
	keep if year==$yr1
	local obs1=_N
	save ${temploc}_junk1,replace
	use ${temploc}_fam
	keep if year==$yr2
	local obs2=_N
	save ${temploc}_junk2,replace
	mac def marker 1
	if `obs2'>`obs1' {
		$runcmnd this.cps `obs1'
	} 
	if `obs2'<`obs1' {
		$runcmnd that.cps `obs2'
	}
	if `obs2'==`obs1' {
		mac def marker 0
		$runcmnd other.cps `obs2'
	}
	mac def hh=$hh+1
}
end
doit `*'

use ${temploc}junk,clear
drop if $y1>0 & $y2>0 & ($y1>1 | $y2>1)
if $marker {
	append using ${temploc}_junk
	drop $guy $group
}
drop $y1 $y2 
save ${temploc}junk,replace

use ${temploc}dummy
drop if $dummy==1
drop $dummy $y1 $y2 $guy $group
replace match_id=year==%yr1
replace match_id=sum(match_id)
replace match_id=match_id + $leftoff
replace level=2*$step
mac def leftoff=match_id[_N]
save ${temploc}dummy,replace
use ${temploc}matched
append using ${temploc}dummy
save ${temploc}matched,replace	
exit 0