When I started college in 1982 as a CS/EE double major, the big-money major was petroleum engineering. If I remember correctly, they lost a lot of people who had done well in high-school when they hit the calculus for engineers classes.
It's just the same now with CS. We lost 75% of CS prospects in the first semester, almost all of them due to Calculus (although I think some of them came in with the malformed idea that programming was just like video games).
I kept in contact with some of the folks who dropped out or switched majors - they're working at convenience stores and the like.
Similarly, when I started in '83, we had a bunch of gonna-be computer scientists at my school. I think about half of those people were gone a year later.
What I don't know is if the proportion of people who stick with it is about the same from year to year, or if the years with massive enrollment increases have much higher attrition rates.
Alas, that graph shows a big peak of CS graduates around 86/87 or so. I didn't get out until 88, after the wave - and the 87 market crash-let. I had to work too much to do my upper division work in 2 years, so it took me 3 - but I got to learn "dBASE" in my intern-like job, which was largely obsolete by the time I finished school. Glad we learned some C in school (even if I liked Pascal better).
