However, as time went on, the station suffered a decline in ratings, especially after the introduction of the Portable People Meter in the Seattle market in 2009.
Lacking the internal expertise to do so – additional outside help from Martin Marietta was sought.
CBS retained the WBBM-FM call letters on 96.3 when WCFS-FM (105.9) converted from adult contemporary to a simulcast of WBBM (AM) on April 1, 2011, as no call letter verification is needed with the Portable People Meter system.
From mid-2004 until the introduction of Arbitron's Portable People Meters (PPMs) to the Chicago radio market in mid-2008, WGCI was the #1 music station and overall radio station in the Chicago radio market.
Nevertheless, the station had a devoted audience, and its ratings were not largely adversely affected by Detroit's switching from Arbitron's diary system to the Portable People Meter PPM.
The format change was likely done due to the introduction of Arbitron's Portable People Meter audience measurement system in the month of June into the Milwaukee market.
Since the advent of the Portable People Meter by Arbitron in Philadelphia, WXTU has become the most listened to country station in the United States (based on listener cume).
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