Before the dot.com bust, for decades MIT's EECS department had 40% of the undergraduates (there's several degrees there, all require some CS and EE, the two rel

Before the dot.com bust, for decades MIT's EECS department had 40% of the undergraduates (there's several degrees there, all require some CS and EE, the two relevant ones would be the CS focused one, 6-3, which few take nowadays, and the one that's sort of split between both, 6-2, which if I remember correctly is now the most common one). That fell by more than 1/2 after the crash, but as of late, like other schools such as Stanford, it's gone back up significantly, fairly close to the old numbers. However the Institute has always keep the department's size proportionately much smaller, like 6% if I remember the '80s figures correctly. That's because history is littered with formerly extremely popular fields like aeronautics which at some point crashed and never returned (aero/astro did so in the early '70s). So even for MIT far less than 10% of its faculty will "ever be in computer science" given your latter interpretation of the phrase and the fact that many EECS faculty are EE types.