What mechanism prevents government organizations from handing out too much money for research during a year with exceptionally good proposals? I'm imagining that people in charge of approving funding go about their business and realize that there's been too many good ideas and they're gonna run out of money before the end of the business cycle if they continue going at this rate, so they dial back and raise standards. However, there should be some ways to quantify this.
Furthermore, they might have to raise standards in an artificial way, creating rejections where the reason is not that there's anything wrong with the proposal, but rather that there's not enough money to go around. In this case, do they write something along the lines of "we couldn't find anything wrong, but money is tight and we received a lot of submissions blah blah blah..." on the rejection letter?