I was wondering if anyone could tell me the differences and similarities of agencies such as Arbitron and Eastlan. How do they come up with such different numbers? Thanks.

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[quote="Neckbeard"]I was wondering if anyone could tell me the differences and similarities of agencies such as Arbitron and Eastlan. How do they come up with such different numbers? Thanks.[/quote]

The best one is no longer in business. Birch. Large sample, phone based.

Nielson was great when they dabbled in Radio. They bailed out in a hurry.

Eastlan is okay but more expensive than Arbitron.....

All ya really got, radio wise, is Arbitron.

Arbitron and Eastlan mostly don't cover the same markets. Eastlan focuses on smaller markets. Broadcasters generally don't have a choice in any given market.

Arbitron uses Personal People Meters (PPMs) in the top 50 markets. It's a small device respondents are supposed to keep with them which records which radio stations are played in the vicinity of the PPM.

In smaller markets, Arbitron sends out diaries. Respondents are supposed to write down what they listen to. The method has been widely criticized as inaccurate (in radio ratings and in other types of studies). Often people fill out the diaries at the end of the week and don't remember correctly. Or they mis-estimate how much they listen to a given station. Or they may try to "help" a station by inflating how much they listen. Outside of Arbitron, diary panels are not used much any more.

Eastlan calls people on the phone and asks them what they listened to yesterday. Difficulties in reaching people on the phone make a truely representative sample chancy. And the phone interview is subject to the same kind of (deliberate or inadvertent) human error as diaries, although recall is likely to be better with prompted questions on the next day. Eastlan also claims lower costs for their surveys.

Another method popular in the past was the telephone coincidental: You call people and ask what they a listening to right now. Again, the problem was reaching people on the phone and this method excluded out-of-home listening.

But as a practical matter, broadcasters don't really have a choice.