Arbitron, the leading radio ratings company, says it will replace listener diaries with people meters. “Arbitron has measured radio station listenership since 1965 by collecting handwritten diaries from volunteers who mail them in. The people meters have been in trials since 2001. The company plans to have the meters in place in the top 10 radio markets by the fall of 2008 and in the top 50 markets by 2010 or 2011.”