From the NY Times:

Ratings Bounce for Radio Stations That Turned to Classic Hip-Hop

By BEN SISARIO DECEMBER 25, 2014 10:00 AM

Two months ago, a Houston radio station changed its format from news to “classic hip-hop” — meaning lots of LL Cool J, Tupac Shakur and the Notorious B.I.G. — and kicked off a broadcasting frenzy.

Since that station, KROI-FM — owned by the Radio One chain and now known as Boom 92 — changed over, big broadcasters around the country like iHeartMedia and Cumulus Media have quickly followed with their own variations on the new format. This week Nielsen released numbers for three of Radio One’s stations, and while the results are promising, there is some cause for concern.

Once its format flipped KROI’s audience more than tripled, going from 245,000 to 802,000, and its share — meaning the percentage of radios in use and tuned to a station — went from 1.0 to 3.2, according to Nielsen. In Philadelphia, WPHI-FM, which became Boom Philly on Nov. 6, grew from 534,000 in the month immediately before the change to 736,000 after. (Radio One had timed that change exactly to Nielsen’s ratings period.) KSOC-FM in Dallas, which turned on Nov. 14, went from 524,000 to 724,000.

Radio executives say that more classic hip-hop stations are expected around the country in the new year. But one piece of data about KROI in Houston throws some cold water on the excitement. Although that station’s audience grew quickly when the new format was introduced, it fell slightly the following month. In the four-week ratings period that began Nov. 6, the station’s audience declined by 2.6 percent to 781,000, and its share dropped from 3.2 to 2.9.

That suggests that after an initial explosion — and a great deal of local and national attention in the news media — some listeners moved on to other things.