On the Arbitron site, there are only four stations listed in the public 12+ ratings. All of them belong to Town Square, which arguably is the king of the hill at the moment. According to Radio-Locator, there are 53 stations that are receivable in my zip code. Even if 1/3 of those don't have a decent enough signal to listen to, that still leaves 35 stations that I can surely get with little or no problem. Many of those unlisted stations are still very good advertising mediums for the right sponsors, even though they are no longer listed in the ratings.
Somehow, ignoring roughly 80-90% of the stations in the market seems like a case of "The Emperor's New Clothes." Presumably, the stations and agencies that subscribe get to see all stations in their proper perspective. I hope so...