<p>Among the top 90 universities, as the freshman class gets bigger, the SAT 25th percentile gets lower. The correlation is a (negative) -.6. (Also true of SAT 75th percentile.)</p>
<p>As the size of the freshman class gets bigger, the difference between the SAT 25th percentile and the SAT 75th percentile also gets bigger. The correlation is +.5.</p>
<p>So, generally, as the freshman class gets bigger, the selectivity of the student body gets somewhat lower and more diverse.</p>
<p>What are the laws of nature that control this? Why is this so?</p>
<p>Why isn't Harvard's freshman class all 1580+ scorers? They probably have enough applicants in this range.</p>
<p>I may have partly answered my own question. A lot of it has to do with the public universities which tend to be larger and more "inclusive" (i.e. somewhat less selective).</p>
<p>But, there is still a tendency among the private universities for the larger privates to be slightly less selective and among public universities for the larger publics to be somewhat less selective.</p>
<p>Indeed...and their reasons for same are often as you suggest, "to be more inclusive", as part of their general overall mission in life. Its admirable, actually. Because we all know that success in college is not based solely on SAT scores and that scores of at least 500CR and 500Math (and higher) are correlative to a high success ratio. Those below that number are mixed results, depending on individual circumstances and maturity.</p>
<p>The entire notion of "selectivity" is an interesting phenomenon and one ponders what gets it started and why? Is it a desire to attract the very best students and hopefully they become rich and famous and donate a lot of money to the school? </p>
<p>Colleges and even state universities all got their start as largely regional schools to provide higher education to the locals. Somewhere along the line it became a rather brutal contact sport. Have you done any research into this?</p>
<p>Are you really Al Gore's cousin?</p>
<p>No, I have not done research on that last question in your post. I just do this as a sort of hobby. I like to play with numbers.</p>
<p>As the size of the freshmen class increases, the bell-shaped curve of SAT scores becomes more representative of the entire population of SAT test-takers. Since the 25th percentiles at top universities are greater than the 25th percentile of the nation, it will drop as the freshmen class grows. Also, since the SAT curve for the nation is much more spread out, increasing the size of the freshmen class will also result in a larger difference between 25th and 75th percentiles.</p>