Nielsen Audio

Arbitron's syndicated radio ratings service collects data by selecting a random sample of a population throughout the United States, primarily in 294 metropolitan areas, using a paper diary service 2‑4 times a year and the Portable People Meter (PPM) electronic audience measurement service 365 days a year.

The term commonly used in the radio industry for these ratings is Arbitron book, a carryover from the era when ratings were published in a softcover report that was mailed to clients. More specifically, in the diary-measured markets these reports were called the "Spring book", "Summer book", "Fall book", and "Winter book". Between these "books", Arbitron releases interim monthly reports called "Arbitrends", which contain data from the previous three months known as "rolling average" reports. The two interim reports would be known, for example, as "Spring, Phase I" and "Spring, Phase II".

Arbitron recruits diary survey respondents to note their listening habits in a seven-day paper diary and mail it back to Arbitron. The respondents are paid a small cash incentive for their participation. Turnaround time for release of data from the end of the survey period is approximately three weeks.

After collection, the data is marketed to radio broadcasters, radio networks, cable TV companies, advertisers, advertising agencies, out-of-home advertising companies, and the online radio industry.[7] Major ratings products include cume (the cumulative number of unique listeners over a period), average quarter hour (AQH Share - the average number of people listening in a given 15‑minute period), time spent listening (TSL), and market breakdowns by age, gender, and race/ethnicity. It is important to understand that the "cume" only counts a listener once, whereas the AQH is a product of "cume" and time spent listening. For example, if you looked into a room and saw Fred and Jane, then 15 minutes later saw Fred with Sara. The "cume" would be 3 (Fred, Jane, Sara) and the AQH would be 2 (an average of two people in the room in a given 15‑minute period).

Responding to requests from its customers — radio broadcasters, ad agencies and advertisers — that expressed their interest in the collection of more accurate ratings data, Arbitron introduced the Portable People Meter (PPM) service in 2007.[8]

The PPM is a wearable portable device, much like a pager or mobile phone, that electronically gathers subaudible codes that identify the source of a broadcast, such as a radio station. Arbitron recruits and compensates a cross-section of consumers to wear the meter for an average of one year and up to two years. The audience estimates generated from each monthly survey is used as the buy/sell currency for radio stations and advertisers/agencies.

As of December 2009, the PPM was measured in 33 media markets, including Houston, Philadelphia, Pittsburgh, New York City, Atlanta, Detroit, Long Island, Middlesex-Somerset-Union, Chicago, Los Angeles, Riverside-San Bernardino, San Francisco, Jacksonville, Baltimore, and San Jose.[9] By 2010, 48 markets are being measured using the PPM.[10][11]