You could maintain the same professor-student ratio, but you wouldn't be able to retain the same professors. If Harvard expanded, it would be less able to maint

You could maintain the same professor-student ratio, but you wouldn't be able to retain the same professors. If Harvard expanded, it would be less able to maintain the 'superstar professor'-professor ratio because other colleges would be able to court the professors away with offers of greater access to better facilities and bigger corner offices with better grad student support.