Professor Robert Entman observes in a 1989 book:

The elites who make most of the national news, are the ones who control policy outcomes in Washington... News reports can advance or undermine the policy proposals they want enacted or privileges they want maintained. The information they provide is tainted.
Walter Karp, Harper's Magazine, 1989:

Very few newspaper stories are the result of reporters digging through files; poring over documents; or interviewing experts, dissenters, or ordinary people. The overwhelming majority of stories are based on official sources — on information provided by members of Congress, presidential aides, and other political insiders.