I was being interviewed for a story on course closures the other day by someone doing a story for the NGF, and I asked him how many courses HAD closed since the recession. He got back to me with a number of just under 1,000, which I think is 18-hole equivalents, over the last ten years.
It sounded like a lot, but that's only 7% of the courses in the U.S. ... probably not enough yet.