<p>One of the “luxuries” available at some (not all) of the most highly selective colleges is the ability to declare or change major pretty much at will, as long as one has passed the major’s prerequisite courses and will be able to complete the major without excessive delay in graduation. This probably requires the colleges in question to maintain extra capacity in each major in order to accommodate changes in student demand, since such changes can happen much more rapidly than tenured faculty turnover will allow reallocating faculty between departments and rearranging other resources among the various departments. So, even if Yale (for example) is under capacity, it may not want to add students in order to maintain the reserve capacity in each major.</p>
<p>State universities and some private universities may have different motivations; any excess capacity may be seen as wasted capacity, so enrolling each major and campus to the limit may be the usual practice. Of course, this can mean competitive admissions processes to declare or change major if the desired major is at full capacity.</p>
<p>An example of what can happen if students are unexpected interested in courses or majors that have insufficient capacity:
<a href=“No Calc 101 for you! - Parents Forum - College Confidential Forums”>http://talk.collegeconfidential.com/parents-forum/1556885-no-calc-101-for-you-p1.html</a>
<a href=“Is anyone else having trouble getting into Intro CS classes? - Math/Computer Science Majors - College Confidential Forums”>http://talk.collegeconfidential.com/math-computer-science-majors/1683380-is-anyone-else-having-trouble-getting-into-intro-cs-classes.html</a></p>