I don't actually think it works like that. I was told by my advisor (who used to read grad school apps at her former school) that there are several rounds in which candidates are evaluated (a top-10 school is likely to get 400-700 applications for 15-25 spots). In the first few rounds, it is about the numbers, but not exclusively. It also matters where you went to school, and what names are underneath your letters of recommendation. In the final decisions, once the pool is narrowed down, they look a lot more at other factors; one professor at the school i will be attending in the fall (top 10) told me that it was in fact my writing sample that carried weight in my case because it was a critique of one of their professors. She also told me that they are really looking for people who will a) be able to design their own research and that are a good investment, meaning that they won't drop out after two years. My advice, therefore, would be to put your energy into a stellar writing sample and solid statement of purpose. Has anyone heard anything similar?