I believe you are working with the CR file. In that file, the woman's variables start with v and the man's variables start with mv, but this does not mean that there is a perfect correspondence between the men's variables and the women's variables. For example, the man's age is mv012 and the woman's age is v012. However, for the men, there are variables mv034b_*, but for women there are NO variables v034b_* . Your "wifemin" line requires changing each v to mv. Your "agediff" line requires changing v012 to mv012, and replacing the "min(....)" with the corrected "wifemin".