Most of the numbers has to do with the economy. With the economy being much less attractive for employment, less people are getting out of the military. Less are voluntarily dropping out of the academy prior to their 3rd year. Some classes like the class of 2013 had approximately 85 more additional graduate BCT than normal. (They had the big swine flu epidemic, so many of the BCT class didn't have to do a lot of BCT, and they were exempt from being dropped). But mostly, it's the economy. And the military will do what they always do. Cut back significantly: Realize in a couple years that they cut back too much: Then push hard to recruit new people.
I do see the academy becoming stricter with things like academic probation and job selection. Currently; as long as you aren't a screw up, and you are qualified, you can become a pilot. Most of that is because, believe it or not, not everyone wants to be a pilot. Many come in saying they do, but once they understand the 10 year commitment and what they've gone through the first 2 years at the academy, they choose differently. I see that changing possibly to having less pilot slots and therefor the higher gpa/opa will be the ones who get the UPT slot.