It will be interesting to see a follow-up analysis that parses out enrollment behavior by subgroup (e.g., by SAT/ACT score) as it will be easier to understand who is choosing not to enroll in college.
Another follow-up could be to see which institutions are losing students. It is known that college enrollment is counter-cyclical to the economy and that enrollment declines at community colleges and open access universities when people can get a job right out of high school.