This study draws on individual-level data from
the PSID, which began in 1968 as a longitudinal
study of a representative sample of U.S.
individuals and their co-residents with an oversampling
of low-income individuals. The PSID
interviewed individuals from families in the
core sample annually from 1968 to 1996, and
then biennially since 1997. In the 1999 wave,
the PSID began to collect information on individuals’
height and weight. Hence, in this study
we draw on four waves of data: 1999, 2001,
2003, and 2005. Our final estimation sample
is an unbalanced panel of individuals aged
18–65 years old, including 17,479 and 19,747
person-year observations for 6,045 men and
6,806 women, respectively, after restricting our
sample to those observations without missing
data in the estimation variables and excluding
women who were pregnant at the time of
interview.