NEW YORK — Government subsidies for the media, which are not widely known but are a long-running source of revenue for publishers, are quietly vanishing just as the industry is struggling to remain commercially viable, according to a new report released Thursday.

The report from the USC Annenberg School for Communication & Journalism in Los Angeles points out that postal subsidies for the publishing industry have dwindled to nearly nothing, and many government agencies are preparing to shift public notice advertisements to the Web, cutting out an important revenue stream for newspapers.

The report was written by David Westphal, a senior fellow at the Annenberg School and former Washington editor for McClatchy Newspapers, and Geoffrey Cowan, Annenberg's dean emeritus and a former director of Voice of America, the federally funded broadcaster.