It's getting harder to distinguish CNN from its more ideological cable news rivals, according to Pew Research Center's annual State of the News Media report.

It may be because of cost-cutting, or an effort to embrace its rivals' greater emphasis on opinion. But between 2007 and 2012, the number of interviews on the channel's evening news programming doubled, while its coverage of live events and story packages fell by 50 percent.

The picture was roughly the same during the day, when CNN's coverage of live daytime events, other than interviews, plunged from 45 percent of its daytime lineup in 2007 to 23 percent in 2012.

Interviews with talking heads are cheaper to produce than sending reporters out to war zones or disaster areas. They also tend to attract more partisan figures, who are often eager to put a Democratic or Republican spin on the day's events.

The end result is a marked increase in the number of opinionated chatter coming across the airwaves, courtesy of the big three cable news players.

Fox News' evening coverage was also dominated by interviews. The highest-rated cable news network didn't change much about its winning formula over the last five years. The number of packages remained roughly stable at 34 percent in 2012, up from 31 in 2007, while interviews accounted for 46 percent of programming, down from 48 percent, and live events accounted for 1 percent of coverage, down from 3 percent in 2007.

On MSNBC's primetime lineup, the number of interviews dropped from a massive 75 percent of programming in 2007 to 52 percent in 2012. The number of packages increased from 13 percent five years ago to 31 percent today, while coverage of live events rose from 1 percent to 3 percent.

Despite the decline in interviews, MSNBC has done the most to ratchet up partisanship, the study found. Its authors say the left-leaning channel devoted 85 percent of airtime to opinion and commentary and 15 percent to factual reporting.

At Fox News, the breakdown was 55 percent commentary and opinion to 45 percent factual reporting, while CNN was the only network to put more reporting than commentary on the air (54 percent to 46 percent).

To come up with its numbers, Pew examined hundreds of hours of weekday programming and thousands of stories from the first five months of 2007 and 2012.

Related Articles:

Jeff Zucker at CNN: Back to Doing What He Does Best?

News Budgets Busted by Cost of Covering Disasters

Chris Hayes Replacing Ed Schultz on MSNBC Primetime Lineup