Here’s something that should come as no surprise. Fewer Americans are relying on radio as their chief source of news. The number of Americans who say radio is their primary news source has dipped from 18 percent in December of 2008 to 16 percent by December 2010, according to the Pew Research Center for People and the Press.

Blame the internet and the convenience it offers of getting the news whenever one wants it.

But here is a surprise. All-news radio is booming.

In Washington, all-news WTOP is the market’s perennial leader, averaging a 10 share. That means that nearly 10 percent of radio listeners in Washington tune in regularly.

Its revenue story is even more impressive. In 2009 the station ranked No. 2 in billing for the entire country with more than $50 million in sales.

The same pattern holds in other markets: WBBM-AM/Chicago, KYW/Philadelphia and KCBS/San Francisco all rank among their markets’ top stations.

What’s driving the growing strength of all-news radio is, of all things, Arbitron’s Portable People Meter for tracking listening.

With the rollout of the PPM across major markets, media buyers are afforded a far more accurate picture of what people listen to, when they listen and how often, all to the benefit of all-news stations.

Under the old diary system, which relies on listeners to remember and write down what stations they listened to, all-news stations got short-changed. Typically, people flip to all-news stations for the headlines, listen for a few minutes, then jump to another station.

When it came to filling out diaries, those short bursts of listening were forgotten about more often than not, and the result was that all-news stations appeared to have lower listening levels than they actually did.

“All-news radio stations are doing great. PPM has treated them well,” says Harvey Nagler, CBS News vice president for radio.

All-news should not be confused with talk radio, though both feature the spoken word. In many ways they are quite opposite.

Talk radio stations rely on a small, loyal following that tunes in for long stretches of time. All-news listeners, though tuning in for short bursts, tune in frequently, and there are lots of them. All-new stations typically have much larger audiences.

Think of all-news radio as like the old CNN Headline News with its rigid format that repeats every 30 minutes. News at the top and bottom of the hour, traffic and weather every 10 minutes with sports, business and other local reporting filling out the clock.

Listeners tune in to catch traffic and weather during their commute or catch up on news, then tune to other stations.

Beyond their big ratings, all-news programming offers several other benefits for advertisers.

The tight format doesn’t allow for lengthy spot breaks. In most cases features are separated by one or two spots at most.

The atmosphere spots run in is also a benefit to advertisers.

“Because it’s a news environment you have an attentive audience and the station’s credibility level is high,” says Michael Young, senior vice president and Pittsburgh market manager for CBS Radio, which includes legendary news/talk station KDKA-AM.

In 2009, KDKA traded afternoon talk programming for an all-news block. Young says that being news-focused in afternoons fits with the station’s mission of delivering the news, then talking about it.

The change has both increased its afternoon ratings and helped drive more occasions of listening to its talk shows.

“A lot of times during the news we’ll be promoting that one of the talk hosts will have more in-depth coverage or a special guest related to the story,” says Young. 

Unfortunately for radio operators, while news stations can be very successful, they are also very expensive to run.

That led Talk Radio Network, one of radio’s leading syndicators, to launch America’s Radio News Network, a series of three-hour all-news blocks stations can insert into their lineup.

TRN is best known for syndicating popular and sometimes controversial talk radio hosts like Michael Savage. Company CEO Mark Masters acknowledges that can provide a challenge for radio sellers. 

But the new news operation. which launched the other day, will be different. The hosts will be reporting the news, not giving opinions, making it safe for advertisers.

“News radio is a 'safe-buy environment,' the type of environment which is usually bought by music or top-of-the-hour news buyers,” said Masters in announcing the new service.

While the PPM ratings bump has been a boon for all-news radio, there still are clouds looming on the horizon; the internet and mobile devices are quickly changing how people consume news.

“There are more people in the market that are competing against radio than ever before,” says Nagler.

For all-news stations to have continued success they will have to press their natural advantages, starting with the content they are already producing.

News stories that on-air might be boiled down to a sound bite can be explored by reporters in-depth online.

 “There are so many new ways to repurpose our content and create more programming with it. We see it as an opportunity to get more listeners and viewers than ever before,” says Nagler.

Radio’s other advantage is being local.

“If there are consumers looking for information in your community, and you have a station branded as news or news/talk which continues to serve the community, you have a great opportunity to establish yourself in the digital world,” says Nagler.