If you think you heard a lot of Hoobastank and Kenny Chesney on the radio last year, you're not alone.
Mediabase, a California based company which specializes in tracking radio station playlists electronically, tallied what eight Syracuse stations played during 2004. The Syracuse Post-Standard has more on which artists got the most air time and also the scoop from several program directors as to how those playlists are put together.
Source (link may no longer work):
www.syracuse.com/entertainment/poststandard/index.ssf?/base/entertainment-8/1106818830116050.xml