number of kids
=1 if mom had more than 2 kids
=1 if 1st kid was a boy
=1 if 2nd kid was a boy
=1 if 1st two kids same sex
=1 if 2nd and 3rd kidss are twins
age of mom at census
moms age when she 1st gave birth
=1 if mom is black
=1 if mom is hispanic
=1 if mom is othrace
did mom work for pay i 1979
moms weeks worked in 1979
hours of work per week in 1979
labor income per week, 1979, constant $