Alright guys, I got bored and decided to look into the numbers. I spent way too long on this, but hopefully it adds value to this discussion.
Here are two charts I made. The first one shows the correlation between the U.S. unemployment rate and the number of AACOMAS applicants. The second one shows the correlation between the number of D.O. schools and the number of AACOMAS applicants.
As you can see, there doesn't seem to be a very strong link between the unemployment rate and the number of applicants. The years that do stand out are 1995-1997, where there was a spike in D.O. applicants, and then 2001-2003, where there was a dip in D.O. applicants. It almost seems like the opposite of what was expected happened, where the number of applicants increased when the economy was better and then decreased when the economy was worse.
The conclusion I came to is that there seems to be a much stronger link between the number of D.O. schools and the number of applicants (makes sense). Since 2003, there's been a steady increase in D.O. applicants. This corresponds with the recent huge increase in new D.O. schools opening. In 2002, the total D.O. enrollment was 9,882 (19 schools). In 2012, this has more than doubled to 20,663 (34 schools). These numbers include branch campuses.
It would've been nice to also include M.D. applicants as well (or just total medical school applicants), but I'm too lazy to do the work required for that now. I uploaded the Excel spreadsheet for anyone that wants to look at the actual numbers.
Sources
1. BLS Unemployment Rate Stats:
http://data.bls.gov/timeseries/LNS14000000
2. AACOMAS Applicant Numbers (before 2007):
http://www.aacom.org/data/applicantsmatriculants/Documents/Applicants by gender 6-17-2011.xls
3. AACOMAS Applicant Trends:
http://www.aacom.org/data/Documents/Trends-apps-enroll-grads.pdf
4. AACOMAS Applicant Numbers (after 2007):
http://www.aacom.org/resources/e-news/ome/2013-02/Pages/Applications.aspx