use individual
sort individid
save individual, replace
use observation
sort observeid
save observation, replace
use membership
drop if (mem_edate != . & mem_edate < $refdate)
drop if (mem_sdate != . & mem_sdate > $refdate)
gen refdate = $refdate
rename mem_sobserveid observeid
duplicates drop individid, force
sort observeid
merge observeid using observation
tab _merge
drop if _merge!=3
drop _merge
rename locationid sociallocid
keep  socialgpid individid sociallocid refdate 
sort individid
format refdate %td
merge individid using individual
tab _merge
drop if _merge != 3 
drop _merge 
rename birthdate bod
drop appround
drop ind_name
duplicates drop individid, force
replace fatherid = "00000000000" if strlen(fatherid) !=11
replace motherid = "00000000000" if strlen(motherid) !=11
save cross\crossmembership, replace
use individual
keep individid birthdate
rename individid fatherid
rename birthdate fbod
save cross\crossfbod, replace
rename fatherid motherid
rename fbod mbod
save cross\crossmbod, replace
close