Cost Per Thousand advertising comparison?

Question

What is a good way to compare the cost per thousand between the various advertising opportunities available to national advertisers?

Answer 1

This is a very complex question.  CPMs for different media measure different things:  the definition of an "impression" is different for each medium.  

If you must have a quantitative analysis, you can proceed with two adjustment factors.  The first reflects the likelihood of a person exposed to the ad actually noticing it.  An ad in daytime TV is about half as likely as in Prime TV to be noticed.  You need research to help you score each medium on the noticing power of each impression.  The second adjustment is the quality of the exposure for your given objectives.  If you have a food product, how much better will a TV exposure accomplish your objectives than a Radio exposure.  You get 60-seconds in a radio spot, but no picture; How import is visual?  With magazines you get picture but no movement.  Even in magazines, a food book reaches the target when they are thinking about food, how important is that?

Adjust each medium's CPM by these two factors to calculate a relative cost-per-thousand effective exposures and then compare.  It far easier to just eliminate media that won't accomplish the objectives then it is to agree on and use such factors, but this type of analysis is common in agency media planning departments.

Answer 2

Comparing CPM (cost per thousand impressions) can be done "side by side" - if you're looking to determine the return you will receive on your investment, then the only way to do that is to test out the source or ask current users about the rate of return they are receiving.