A report released Friday by ad buyer Magna Global found that ratings during prime-time commercial pods were 7 percent lower than the programs they aired in. On cable, the commercial pods averaged 11 percent lower ratings.

The Magna report found that pods on CBS declined the least among the broadcasters, while its corporate sibling UPN had the biggest drops.

Court TV, Bravo and Fox News had the least falloff among cable networks.

The study also looked at data on digital video recorders and found that about 75 percent of commercials get skipped during playback. Magna has been a vocal proponent of buying ads based on live viewing ratings from Nielsen Media Research rather than on the live-plus-same-day or live-plus-seven-day measures that include DVR playback.

The report, written by Steve Sternberg, executive VP of audience analysis, concluded that at this point minute ratings shouldn’t be used as a currency for ad buying because of a lack of consistency across multiple episodes of the same program. He said more sub-minute research was required.