&quot;married&quot; is an
indicator for married (1=married, 0=not married).
</p>
</li>
<li><p> &quot;nodegree&quot; is an
indicator for whether the individual has a high school degree (1=no degree,
0=degree).
</p>
</li>
<li><p> &quot;re74&quot; is income in 1974, in U.S. dollars.
</p>
</li>
<li><p> &quot;re75&quot; is
income in 1975, in U.S. dollars.
</p>
</li>
<li><p> &quot;re78&quot; is income in 1978, in U.S.
dollars. </p>
</li></ul>

<p>&quot;treat&quot; is the treatment variable, &quot;re78&quot; is th