And magnifying the problem, for many chains, is a heavy burden of debt that they took on, mostly in a spree of buying other newspapers from 2005 to 2007, just before the bottom dropped out of the business.

The Tribune Company, for instance, owner of The Chicago Tribune, The Los Angeles Times and other papers, filed for bankruptcy in December, largely because of its debt load. The reality is that even though the economic climate is hard for newspapers, without their debt payments the publishers in bankruptcy would still make money, as do most newspapers around the country.

But profits are shrinking fast; taken together, major chains had an operating profit margin of about 10 percent in 2008, down from more than 20 percent as recently as 2004, according to research by John Morton, an independent analyst.

The recent closures and threatened closures point to an ominous new trend. For The Chronicle, The Rocky, The Star-Ledger, The Citizen and others, debt was never the problem and they belonged to solvent companies, but still they have been losing money.

Analysts say that many other major papers have also slid into red ink recently, including The Washington Post and The Boston Globe (which is owned by The New York Times Company).

The steady trickle of downsizing that sapped American papers for almost a decade has become a flood in the last few years. The Los Angeles Times still has one of the largest news staffs in the country, about 600 people, but it was twice as big in the late 1990s. The Washington Post had a newsroom of more than 900 six years ago, and has fewer than 700 now. The Gannett Company, the largest newspaper publisher in the country, eliminated more than 8,300 jobs in 2007 and 2008, or 22 percent of the total.

Image The Star Tribune, the leading daily in Minneapolis, filed for bankruptcy in January. Credit... Ben Garvin for The New York Times

On Wednesday, The Miami Herald, once the celebrated flagship of the Knight Ridder chain, said it would trim an additional 19 percent of its already diminished staff.