I constantly hear about CPM (Cost Per Thousand) rate comparisons between online and offline media. It’s like comparing apples and cereal. And, it’s not as if these comparisons are being made by non-media people; they should know better. This only serves to complicate things for buyers and the industry at large. Let’s look at the pieces:
Audience vs. Watchers or Listeners
In broadcast, television and radio, CPM represents audience members based on differing means of measurement. Diaries and metres are the two most common. Measurement methodology aside, (that’s a whole other blog post) this means that CPM is based on the number of people that are supposedly tuned in to a program and therefore the ad in question. Of course, no one really knows if anyone was in the room. Anyway, the broadcast CPM represents 1000 audience members. Odds are that the actual number of watchers or listeners is significantly less than that.
Readership vs. Readers
In the print world of newspapers and magazines, the CPM is the readership number. The readership of a print product is usually measured through a survey, conducted a couple of times per year that collects information on reading habits. Readership numbers are most often a multiple on the number of purchased copies. For example, if 100 people subscribe to a magazine and on average 2.5 people read a copy, then the readership is 250. Again, no one really knows if anyone even opened their newspaper or magazine. So, when buying print media on a CPM basis, you’re buying assumed readership not readers.
Readers vs. Impressions
Online is a totally different ball game. Throw surveys, metres and diaries out the window – the online unit of measure is the ad impression. Yes, it’s a very accurate means of measure, but it’s not readers that are being measured. An ad impression is counted each time the ad shows up on the web page. A single user may be exposed to the same ad multiple times, sometimes on the same page with different ad units.
In Conclusion
Comparing these three very different measurements and effectively different things is useless. It seems the expedient way to compare media spend, but it really does not help anyone, and in fact it hurts. It hurts buyers because they are deluded into thinking that they can equate CPM’s and therefore make educated decisions. As an industry, we need to stop confusing the issue with inaccurate comparisons.
