ed mean is used
when the information of hours of work as the weight
is available. The mean hourly wage could also be a predicted
value if the original value is considered influential
by the robust linear regression as part of data cleaning.</p></dd>
<dt>age_1979</dt><dd><p>The age of the subject in 1979.</p></dd>
<dt>gender</dt><dd><p>Gender of the subject, FEMALE and MALE.</p></dd>
<dt>race</dt><dd><p>Race of the subject, NON-BLACK,NON-HISPANIC; HISPANIC; BLACK.</p></dd>
<dt>hgc</dt><dd><p>Highest grade co