For some reason, we're also manipulating the numbers to make our enrollment appear larger.
I suspect most people look at that 56,6xx number and think it's just CS and maybe even just the undergrad population, but it also includes Galveston, Qatar, law school, vet school, and the graduate students. It wouldn't surprise me if they included the medical school this year.
Pull out:
Galveston - 2000
Qatar - 600
Law School - 700
Graduate Students in CS - 10,000
That leaves ~43,000 undergrad students in CS. Fall '99 we had ~36,000 undergrads. So we've grown ~20% in 15 years which really isn't a dramatic growth.
UT's undergrad population is ~40,000, but it has only grown ~10% in the last 15 years. They've also had their special top 10% rule for the past 5 years which has limited growth.