Keep in mind that it can only be accessed from a SWSIII.
Click on the "Advancement lists, Cuttoffs, and Stats" button and you can select which years stats you want to view.
I've noticed the average has been steadily increasing due to the increase of people taking the test. A few years ago, the average number of eligible people who took the SWE was in the the 30 to 40 range. When I took the May '07, there were over 80 who competed.
Actually, you can access the stats and cutoff msgs on any computer...the only thing that you need a WSIII for is the actual placement lists... http://www.uscg.mil/hq/psc/adv.asp