A new study from the University of Chicago finds that newspaper owners and editors are more sensitive to market forces than to personal ideology in determining how they present the news.

The prospect that newspapers are good at writing to their audience in an effort to maintain circulation might seem obvious to some. But the study, “What Drives Media Slant? Evidence From U.S. Daily Newspapers,” has implications for press watchdogs, courts, and legislators fighting to limit or diversify the ownership of news outlets across the country.

The co-authors of the paper, University of Chicago economists Jesse Shapiro and Matthew Gentzkow, say that when it comes right down to it, the press is an open market like any other. “You can measure the news media on several dimensions,” Mr. Shapiro said. “We were interested in the ideological dimension. What shapes political news coverage.” What they found was that the public largely drives how the news is covered. A common perception of newspaper chains is that the owners and editors set the editorial “slant.” But the newspaper market is more efficient than commonly thought: When news coverage caters to the tastes of owners instead of readers, they become significantly less profitable, the study shows.

It found that newspapers of profitable, large chains vary in their editorial slant, despite long-held beliefs that chain publications were largely indistinguishable.

“We’re only beginning to investigate the many ways the media can have important consequences on society,” Mr. Shapiro said. His papers are bringing Mr. Shapiro renown not only for their outstanding scholarship but because he is just 27. He is a native of Brooklyn and the valedictorian of his Stuyvesant High School class. Messrs. Shapiro and Gentzkow devised innovative metrics to measure what sorts of circumstances favor an open and competitive press market. One of the hallmarks of the study is how its authors determined slant. They looked at every two-word and three-word phrase in the 2005 Congressional Record and skimmed off 100 or so of the most frequently used terms.

They also looked at how 700 American newspapers used language to describe certain social and political terms, which allowed them to characterize the reporting as more in line with Democrats or Republicans.

Terms such as “death tax” and “war on terror” suggested a Republican slant; “estate tax” and “war in Iraq” suggested that the newspaper slanted toward the Democrats. Not surprisingly, the study found that newspapers like the New York Times and San Francisco Chronicle slanted left; the Wall Street Journal and Washington Times slanted right. (The economists did not include The New York Sun in the study.)

Built into their model is the ability to determine what it costs a newspaper to stray a single, predetermined unit (one standard deviation, as statisticians would say) from the established politics of the newspaper’s readers. The broad answer: Circulation (and, therefore, variable profits) would fall 3.4%.

The report uses the Washington Post, which it determined to be editorially left-of-center, as an interesting case in point. What it supposes is that it would cost the Post more than 3.4% of variable profits to maintain a staff of reporters and editors to fall in line with its new political slant.

The cost of refining the tastes of its reporters’ politics serves as an example of a startling wage effect. The big picture: Newspapers that cater to the political tastes of their readers and maintain staffs of editors and reporters generally in line with “reader slant” are more profitable and run more efficiently.

Based on research by Mr. Gentzkow, the Washington Post had variable profits of some $500 million in 2004. The study assumes the average annual reporter’s salary to be $75,000 and an editor’s to be $125,000. “Probably an overestimate,” the paper notes. So, assuming the Post paid $43 million in editorial salaries, the newspaper couldn’t afford to hire a new staff in line with its new slant even if it were willing to boost that payroll by 41%, according to the paper. (For Sun readers following the math, it’s (500/43)*3.5%=41%.)

The study says it illustrates “[that consumer demand responds strongly to the fit between a newspaper’s slant and the ideology of its potential readers, implying an economic incentive for newspapers to tailor their slant to the ideological predispositions of consumers.”