The Encoder

To be electronically measured for ratings, radio stations (both Arbitron subscribers and non-subscribers) are eligible to receive free encoders that send out continuous silent audio signals. The Portable People Meters are worn by survey panelists and detect the transmitted inaudible codes. A Radio Broadcast Company has to inform Arbitron on the number of stations owned.

There will be two encoders sent to each station. One will be activated and placed in the transmitter rack; the other serves as a backup. For individual recognition, each station gets an ID code, which is transmitted within the silent audio signal. Upon request, separate encoders will be sent to stations wishing to separately market other forms of digital audio, such as Internet, podcasts, or HD stations. Sirius/XM satellite radio will also be provided encoders for measurement. Although the encoders are free for radio broadcasters, only Arbitron subscribers can use the ratings results for sales or marketing.

Survey Panel Selection

The methodology for selection is the same as for Arbitron's paper diary markets: households are randomly chosen to serve on Portable People Meter panels, with family members referred to as panelists. The socio-demographic composition, age, sex, and race, determine the number of panelists for the sample size of a market. Arbitron uses information provided by the U.S Census Bureau for electronic measurement. Panels are built through the use of zip codes with listed landline phone numbers and cell phone-only households.

(An exception is Houston, where there is also door to door canvassing included in the process. About one third of the entire market panel is chosen in this fashion. There are no current plans to incorporate the same procedure in any other Portable People Meter markets.)

In search of panelists, Arbitron uses an automated system to contact landline households. The automation has a built-in formula to reach unlisted numbers. Since using automation/autodialers to contact cell phones is illegal, Arbitron applies a “brute force” method to find cell phone-only (CPO) households. This means pulling a sample of cell phone numbers, and calling in an attempt to reach someone. When a person answers, the caller asks whether he or she has a landline. If they do not, it is a cell phone-only household, and can later go through the PPM process for possible selection to a panel. However, a more efficient method for finding CPO households is on the horizon for diaries and the Portable People Meter (PPM).

Arbitron's Ed Cohen, Ph.D., Vice President of Research Policy and Communication, says:

“It’s pretty simple. We’ll use an address frame (as we used in Houston PPM). From that, we pull a sample and match as many addresses as possible to landline phone numbers. These addresses are removed. The remainder is sent a short survey with some upfront cash and the promise of more for completing the survey. Those that are CPO become the sample pools. Language is included in the questionnaire that allows us to be in compliance with the Telephone Consumer Protection Act of 1991 (use of autodialers to call known cell phones).

“That’s how we will put CPO into the diary service. We are going to test the same system for PPM and transition PPM CPO to that system assuming no problems.”

Panelists can serve from six months up to two years, and are provided cash and other incentives to participate. Much like in airline mileage programs, points are awarded if certain compliance requirements are met or exceeded. New households are transitioned to replace those phased out or dropped from the panel.

The next series installment will address the meter, panelists' instructions, motion, and listening.