PROVIDENCE – Television stations in the Providence-New Bedford market saw their advertising sales drop 11.8 percent last year, nearly double the national average, according to a new report.

Total ad revenue for Providence-New Bedford TV stations fell $8.9 million in 2008 to $66.6 million, down from $75.5 million in 2007 and $97 million in 2006, according to a report on television markets nationwide by BIA Financial Network Inc., a Chantilly, Va.-based market research firm.

Although 2006 was a particularly lucrative year for local advertisers, as politicians in competitive races spent heavily on TV ads to reach voters and the state was faced with a ballot measure to create a casino in West Warwick by the Narragansett Indian Tribe, the trend is still downward. Excluding 2006, annual TV advertising sales in the Providence-New Bedford market averaged $81.38 million from 2003 to 2007, whereas 2008 revenue was 18.2 percent below that figure.

WPRI-TV (CBS 12) suffered the biggest drop in 2008, according to the report, which said the station’s revenue was down 14.4 percent from the previous year, falling to $15.88 million.

Double-digit declines were also posted last year at WNAC-TV (Fox 64), which saw ad revenue fall 11.9 percent to $9.85 million; market leader WJAR-TV (NBC 10), at which sales fell 11.3 percent to $28.48 million; and WLWC-TV (CW 28), which saw sales fall 11 percent to $3.65 million.

The report also said there were smaller advertising sales drops at WLNE-TV (ABC 6), with a revenue decline of 8.9 percent to $8.23 million, and Block Island-based WPXQ-TV (Ion 17), which saw sales fall 5.3 percent to $450,000. The report did not offer figures for public television station WSBE-TV (PBS 36) or local cable channels.

TV stations’ revenue fell an average of 6 percent nationwide last year, the report said, as carmakers and retailers pulled back on advertising spending. Mark R. Fratrik, vice president of the research firm’s BIA Advisory Services division, said TV ad sales “are now beginning a dramatic downward shift.”

Geoff Klapisch, a media and advertising professor at Boston University, told The Boston Globe that the report’s findings were evidence of a changing advertising market. “Advertisers and marketers are getting smarter every year, and they are finding other places to put their money,” Klapisch said.

WJAR continued to dominate the local market in 2008, capturing nearly 43 percent of the region’s total ad revenue. The station, which has been forced to cut jobs in recent months, is owned by Media General Inc.

Trailing WJAR was WPRI, owned by Providence-based LIN TV Corp., with 24 percent of local revenue; WNAC, operated by LIN TV, with 15 percent; and WLNE, owned by Global Broadcasting LLC, with 12 percent.

The report also offered a gloomy forecast of the stations’ expected advertising revenue over the next decade, predicting total sales will shrink by another 13 percent this year to $57.9 million and remain under $60 million annually until 2012.

Additional information on BIA Financial Network Inc. and its quarterly report, “Investing in Television,” is available at BIA.com.