Manually completed diaries were the first method by which broadcast media information was recorded, including what radio stations and television channels people listened to and watched. Arbitron conducted surveys where it became the consumers’ jobs to keep a log of exactly what radio stations they tuned into and for how long they stayed on that station. After stations complained that the reports generated from diary data were incorrect due to the high probability of human error, in 2007 Arbitron announced the creation of a passive and electronic way of measuring listenership, otherwise known as, the Portable People Meter.
The Portable People Meter, or PPM, was designed to meet the challenges of the expensive transition to digital broadcasting as well as the convergence of media and the internet. It has acted as an answer to audience researchers who have had to convince an ever-reluctant audience to take part in ratings and consumer surveys. Participants are randomly selected, just as they were for the diary method. Survey participants (ages 6+) simply have to wear or carry the meter with them, keep the green light on, which indicates the meter is in motion, and dock the meter at bedtime.
PPM units act like an ear of a person with average hearing. Every participating radio station has at least one encoder which tags transmitted audio signal that is analog or digital with an audible, but masked code, which is “listened” for and recorded by any PPM receiver unit. It saves the strongest available transmission identifier every 30 seconds. When the meter is docked, the device charges and sends information the data collector which then sends the information to Arbitron nightly.
According to Arbitron’s “Guide to Understanding and Using PPM Data,” the follow nine measures were constructed to ensure that the data collected is as accurate as possible.
- Compliance Rate: The percentage of PPM panelists eligible to be included in the In-Tab sample.
- Designated Delivery Index (DDI): A measure of sample delivery that indicates how the PPM service delivers specific demographic groups, such as race/ethnicity and age. 100 DDI is considered ideal.
- Household (Basic Household): The first group of households selected for inclusion in the PPM panel.
- Household (Alternate Household): A backup group of households selected for inclusion in the PPM panel should any of the Basic Households decline to participate. Alternate Households are within geographic proximity and have similar demographic characteristics to Basic Households.
- In-Tab Rate: The percentage of installed PPM panelists who carry their meters for a sufficient amount of time (eight hours for Adults 18+, 5 hours for children 6 to 17) to be included in the audience tabulations (In-Tab).
- Panel Performance: Method of determining how well the PPM panel reflects the market.
- Proportionality Index: A report that measures how the proportion of a specific PPM demo compares to the percentage of the population represented by that demographic.
- Sample Performance Index (SPI): A measure used as a substitute for Response Rate in some panel design applications and for television meter panels.
- Target In-Tab Rate: Not all PPM panelists can be expected to wear a meter every day or be counted every day in a survey period, so Arbitron has placed enough meters to ensure that a 75% Daily In-Tab Rate on a person age six or older basis will create a statistically reliable sample.
Finally, Arbitron reports Average Quarter-Hour Rating, Cume and Time Spent Listening to radio stations who can then evaluate their performance. This information has helped radio stations re-invent their programming in some cases so it is more in tuned to what their listeners like. Although re-programming can be costly for stations, overall it will boost their performance and the happiness of their listeners.
For more information on the: Advantages of the Portable People Meter System
For more information on how PPMs have helped radio stations improve: PPM: Radio Programming For Heavy Listeners
For more information on the start of PPMs: Press Release: Arbitron Updates Portable People Meter Rollout