We specified marital status as married, divorced,
single, and widowed. Education level
was recorded as a continuous variable from
0 to 17 years and we categorized it as less
than a high-school diploma or general equivalency
diploma (GED), high-school diploma or
GED, and more than a high-school diploma or
GED. Total family12-month income during the
past year was recorded as continuous with
increments of $999.99 up to $49 999 and
then $50 000 and more. We further categorized
income as $0 to $14 999, $15 000 to
$24 999, and $25 000 or more.