The sample is drawn from the American Community Survey (ACS PUMS 2014) were the panel structure is slightly different in comparison to the "classic" structure. Overall 662,775 married women in \(N = 51\) states were observed. Since each state is of different population size, this results in a highly unbalanced panel were the largest state consists of \(T_{max} = 74,752\) and the smallest of \(T_{min} = 855\) married women.
acs
A data frame with 662,775 rows:
state identifier
age of woman
indicates if a woman gave birth to a child within the past 12 months
total persons income
labor force participation
American Community Survey. https://www.census.gov.