This is a very good question. If you want a short answer, I'll tell you that *no, American news articles are not using anonymous sources more than they were 100 or 200 years ago. They might, however, be using more anonymous sources than they did 30 years ago. If you're interested in the topic, Matt Carlson's 2011 book, On Condition of Anonymity: Unnamed Sources and the Battle for Journalism is a good one.

Until the early 20th century, anonymity was the rule, rather than the exception. In the earliest years of the Republic, when Alexander Hamilton, James Madison, and John Jay wrote the Federalist Papers and had them published in American newspapers, they wrote under the pseudonym "Publius." Most newspaper writers stayed anonymous, even into the middle of the 19th century, and their sources generally stayed anonymous as well. It's easier to talk to people when they know they won't be outed for their views, and if you examine early newspapers, you'll see dispatches written as unsigned letters with few direct quotations. Take this 170-year-old edition of the New York Herald as a typical example.

This led to some really big political and social fights. As Carlson explains, "Congress conducted hundreds of leak investigations, even confining a New York Herald reporter to a room in the Capitol for leaking a still-secret treaty with Mexico in 1848." Journalists didn't typically publish their sources, but they frequently cooperated with courts when pressured -- there was much less of an idea that the media should be protected from government or political pressure.

Starting in the 1830s, a handful of newspapers and news writers started labeling themselves by signing their reports with a byline. This trend rapidly accelerated during the American Civil War when the Army of the Potomac, in an attempt to encourage accurate reporting and accountability, began requiring journalists to publish their names alongside their accounts of events. The Civil War also encouraged the development of journalistic standards and practices. The development of the Associated Press during this time was perhaps the biggest single motivator. As a universal distributor -- it had to serve all its member newspapers equally -- it became the standard by which newspaper coverage was measured.

In the latter part of the 19th century, massive East Coast newspapers competed with each other for readership. Publishers demanded the most up-to-date, most salacious content, and they wanted to hire the best writers as well. Named journalists became important to the reputation of the newspaper, and anonymity took a back seat when it came to writing.

Anonymity among sources stayed relatively high by contemporary standards. That began to change at the end of the century and the start of the 20th century with the development of journalism schools. In 1899, the world's first journalism school opened in Paris, France. Joseph Pulitzer, publisher of the New York World, had attempted to establish a journalism school (at Columbia University) as early as 1892, but the school turned down his money, believing that journalism was too low for a university to study.

He convinced the University of Missouri to open a journalism school (America's first) in 1908. Columbia accepted Pulitzer's money in 1912, opening a journalism school that year. Journalism departments sprang up at other universities (some opening before Missouri's separate school).

As journalism became professionalized, there became an emphasis on methods, quality, and standardization, much as was happening in other industries within the United States. Practices encouraging anonymity were phased out (or at the very least discouraged).

At the same time, however, there were forces working in the opposite direction. Even as journalism schools were being established, anonymous sources were an important window into the presidential administration of Theodore Roosevelt. Especially when it came to telling the story of Congress and the president, anonymous sources from leakers became "a well-established institution in American politics," according to the historian Daniel Boorstin.

In 1970, Daniel Ellsberg's publishing of the Pentagon Papers came from an anonymous source. And in 1972, Mark Felt (labeled Deep Throat) anonymously provided tips that led to the Watergate investigation and the resignation of President Richard Nixon. But even before Mark Felt spoke to Bob Woodward and Carl Bernstein, the U.S. Supreme Court decided the case Branzburg v. Hayes. In that case, the court ruled 5-4 that the First Amendment did not protect journalists from being forced to testify in court about their sources.

The decision has subsequently been watered down, but it had a noticeable cooling effect on the use of anonymous sources. Journalistic mistakes also led to a reduction in the use of anonymous sources.

In 1980, the Washington Post published a sensational story about an 8-year-old heroin addict. The Post refused to reveal the boy's whereabouts, and the story went on to win a Pulitzer Prize, but it was soon revealed that the author of the story had made it up. There was no 8-year-old heroin addict. As the Columbia Journalism Review wrote:

"Probably the biggest change wrought by the Cooke affair was the way reporters were allowed to use and manage unnamed sources. Prior to Cooke, reporters were trusted, the way Woodward was with Deep Throat — nobody asked for his identity. In the months following the Cooke affair, however, that practice began to change, recalls Jim Romenesko, a longtime observer of journalism. In the years to come, Romenesko posted on his site a number of memos from newspapers, including USA Today, declaring a new policy in which reporters were required to share the identities of unnamed sources with an editor. This practice remains an industry standard."

As distance from the Cooke affair has grown, the use of anonymous sources has risen. There are a number of reasons for that rise, but it's pretty clear that there is no straight-line steady rise over the past 200 years. The use of anonymous sources has risen and fallen based upon the needs of the public and journalistic practices.