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<p>There likely is, although the practical limit now (which we are probably at in the US) is probably imposed by the (lack of) quality in K-12 education.</p>
<p>But that is not the point. The non-college-educated people do benefit from having more college educated people around, since the latter have more money to spend, creating more jobs and better pay for the non-college-educated people, so it is not the case that only those who go to college benefit from going to college. Of course, one may or may not agree that this benefit is worth the taxation to subsidize more people going to college (i.e. at the current level of 30% BA/BS attainment rather than the lower level, perhaps as low as 10%, that would otherwise exist).</p>
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<p>It appears to be generally true, although more in a reactive sense (reduced tax revenues forcing cuts, often disproportionately to post-secondary education due to other parts of the budget being higher priority) than due to an intention to privatize the public universities.</p>