<p>You can see the enrollment numbers for each major for the past ten years [url=<a href=“Statistics & Reports | MIT Registrar”>Statistics & Reports | MIT Registrar]here[/url</a>] (I linked the most recent one; the rest can be found in that directory).</p>
<p>MIT doesn’t do anything to ensure that there will be constant numbers of students in each department. Individual departments will do more or less active recruitment of undergraduate majors depending on their inclinations</p>