That's kind of a vague question because the competitive level changes often. Not to mention that this is only one of the MANY things the board takes into consideration when looking at your application.
If you're trying to see where you would rank compared to others on this site, go to the Stats and Scores forum, and check out everyone that has posted. Then, you can compare yourself to others (if you have already taken the ASTB), or you can see where you need to be in order to stay at a competitive level. But remember, an 80 on the ASTB does not guarantee you a spot as an Aviator (if that's what you're looking to be). You have to be well-rounded. Study hard for the ASTB, because it is a long test, with little time to complete some sections.
D