Defenders of PPM argue that lower PPM listening levels prove that diary keepers over-report their listening. Recent research suggests just the opposite. It is quite possible that diary keepers actually under-report their listening.
As reported by cnet here, a report issued by Forrester shows weekly usage of radio along with television, the Internet, newspapers, and magazines. The numbers were gathered from a self- administered survey of 40,000 Americans.
The study is interesting for a number of reasons. First, the study is consistent with other studies that show that television has not been negatively impacted by the growth of the Internet. From 2004 to 2009, self-reported Internet hours grew 117% while television suffered no loss of viewership. Media usage is not a zero-sum game. Growth in new media usage does not require a decline in other media usage.
What caught our attention was the radio listening numbers. According to Forrester, radio suffered non-stop erosion for four years. Self-reported listening had an up-tick in 2008, and then fell back to 2007 levels.
The participants put their radio listening at less than 7 hours per week.
Let’s think about that 7 hours per week. According to Arbitron, average 12+ TSL in the 94 continuously measured markets was 19 hours per week for the last all-diary book. PPM TSLs are lower, somewhere around 12 hours, but considerably higher than Forrester's 7 hours.
The Forrester numbers, based on self-reported estimates, are over 40% lower than Arbitron’s PPM estimates. People think they are listening to less radio than they actually are.
If you doubt that, then take a look at Ball State’s Video Consumer Mapping Study. We reported on the findings here. Their conclusion was:
Serious caution needs to be applied in interpreting self-report data of media use....TV’s self-report tended to understate the actual observed exposure. Computer duration tended to be a little overstated.
While the report gives little attention to radio, radio use was measured along with the other media. Like television, radio use was understated. People estimated their daily listening at about 90 minutes, and they actually listened over 100 minutes. That works out to be nearly 12 hours per week. Keep in mind that this was a video study, so radio was incidental to the focus of the research, yet observers still logged 100 minutes of listening per day.
So in a study that compared a person’s actual radio listening to the amount of time people claimed to listen to the radio, people under-reported their listening by 40%. It may be just coincidental, but the difference between the diary’s 19 hours and PPM’s 12 hours is 40%. These facts suggest that electronic measurement that captured all radio listening could add up to significantly more than 19 hours a week.
Perhaps the diary is under-estimating radio listening, but closer to the truth than PPM.