Last week Ad Age posted the spot prices for the new Fall’s season, based on a “survey of media buying firms.” Combining this information with ratings data for the top 20 programs I compiled approximate CPMs (Cost per Thousand) for the overall audience and the 18-49 demographic.

Most advertisers are not focused on overall audience, since they have far more precise targets for their products or services. In many cases, they also target younger viewers since it’s generally accepted that they’re psychologically they’re less set in their purchasing decisions and more likely to be swayed by marketing messages. This focus on younger viewers has been criticized as “simplistic” by CBS CEO Les Moonves, motivated perhaps to CBS’s dominance of the general audience market. Out of the 20 shows in the following list, 12 are on CBS.

Moreover, popular CBS programs such as NCIS, Criminal Minds and 60 Minutes come up with the lowest CPMs. On average CBS shows have a CPM of $9.76, about 10% less than the group average. Given this access to mass audiences and a efficient broad buy, some budget conscious advertisers opt for CBS:

Donna Spurrier runs Spurrier Media Group, which places ads for companies. One client, Identity Guard, which helps consumers ward off ID thieves, had a small ad budget and chose CBS because it has large numbers of loyal viewers. “When you have a limited budget, you have to fish where the fish are,” she says.

Within the 18-49 demographic CBS’ share of the market is not as strong. The network still lands the most spots, with eight shows in the top 20, while each of the other three networks have four shows each. This information should be taken with a grain of salt however since cue to data limitations for the 18-49 demographic I had to base my analysis on only two weeks of ratings during the month of October. In any case, CBS still seems to be the bargain in this demo, offering a $28.68 CPM, 9% below the average CPM of $31.49.

However, this CPM comparison is by no means the complete story. Advertisers could be interested in much smaller demographic targets which are not being compared above. If they’re targeting younger audiences a show like Family Guy could be more pertinent and more cost efficient. If an advertiser wants sophisticated audiences an investment in The Office or Grey’s Anatomy may make more sense. The latter scenario also ties into the limits of demographic targeting. As I mentioned before, many advertisers are interested in precise targeting, which may go beyond  the limits of age and sex demographics. As one advertiser explained in AdWeek, women 18-34 can mean one thing in New York City and something else entirely in Minneapolis. Therefore, CPM comparisons would be much more refined than what you normally see on a ratings measurement.

Another issue that a standard CPM comparison doesn’t account for is DVR resistance which is why NBC Sunday Night Football ranks so high in these two lists. Sports programs normally assure live viewing thus resulting in a price premium compared to other programs in the same time period. The apt attention of sports viewers is related to another issue affecting TV ad pricing called engagement, which is defined as “how closely viewers are paying attention to the programs.” At a certain level, engagement has already been priced into television slots. Higher attention in primetime is one reason why CPMs are higher there than in daytime. The industry is simply measuring this engagement more precisely now, which may lend it greater weight in commercial pricing standards in the future. But measurement, as they say, is another story.