240 units (rows) and 10 variables (columns). The columns are:
treat
: A binary treatment variable. Equal to 1 if treated in the National Supported Work Demonstration; equal to 0 otherwise.
age
: age in years.
educ
: years of education.
black
: an indicator variable, equal to 1 only if the subject is black.
hispan
: an indicator variable, equal to 1 only if the subject is hispanic.
married
: an indicator variable, equal to 1 only if the subject is married.
nodegree
: an indicator variable, equal to 1 only if the subject does not have a degree.
re74
: earnings in 1974.
re75
: earnings in 1975.
subclass
: The subclass denoting the pairs within the matched dataset.