For the better part of a decade, radio stations aimed at black audiences have dominated the ratings in the Washington area. Arbitron's spring ratings for this market show black-oriented stations in four of the top six spots in total audience -- WPGC 95.5-FM, WMMJ 102.3-FM, WKYS 93.9-FM and WHUR 96.3-FM. Only all-news WTOP and classical WGMS break the pattern.

If radio remains one of the most segregated places in society -- generally speaking, black people listen to black stations, Hispanics listen to Spanish-language stations and whites listen to other stations -- then how do black stations win in a market that is only 26 percent black?

The answer, according to ratings surveys, is that African Americans listen to a lot more radio than other ethnic groups. Blacks listen for longer stretches of time, and listen more at home than do other listeners. A disproportionate number of blacks listen to radio in the evenings and overnight, according to Black Radio Today, a study released this spring by Arbitron.

Radio is more a part of the daily home life of blacks: While only 39 percent of all listening is done at home, blacks do 49 percent of their listening at home. Whites tend to listen more in the car or at work, where there are fewer choices of entertainment and information.

As radio listening has declined over the past few years, bowing to competition from the Internet, MP3s, cable TV and satellite radio, the dominance of black stations has increased in many big-city markets. (Washington has the third largest black population among metro areas, after New York and Chicago, according to census figures.) The average share -- the percentage of listeners tuned to a station -- won by black stations in big markets jumped from 8 to 17 between 1999 and 2003.

Arbitron's analysis shows that black listeners' favorite formats are urban contemporary (hip-hop, like WKYS), urban adult contemporary (R&B and old school, like WMMJ), rhythmic contemporary (hip-hop top hits, like WPGC) and religious (gospel, like WYCB and WPGC-AM).

Nationwide, radio listening is so segregated that while blacks make up 82 percent of the audience of urban contemporary stations, they are only 2 percent of the audience of rock and country stations and only 4 percent of the listeners of classical stations, according to Arbitron's study.

The only formats for which the ratings company found much of a racial mix in audience are pop hits (20 percent of listeners are black), news-talk (8 percent black) and the easy-listening format known as smooth jazz (38 percent black).