Adsense/YPN - do they count impressions differently?

The numbers seem to indicate they might

[midwestadsenseguy]

I've taken one of our more popular pages and converted it over to YPN. All the rest run Adsense. On the YPN page the CTR is about 15% of what the Adsense ads are. At first I thought it may be the quality of advertisers or lack of different advertisers. But after a bit more examination I can't really see the logic behind why the CTR would be so different. Then I thought... perhaps adsense is counting the entire ad block as one impression and YPN counts each indvidual ad IN the ad block as one impression.

So if I have two ad units with, four ads; adsense would count them as 2 impressions but YPN would count the same configuration as 8 impressions. Is it possible that could explain the huge difference in CTR between the two? Other than that, I have no clue... I could see maybe 50% of the CTR given the ad quality but I just can't explain 15% of the CTR any other way.

[kidbuu]

Compare the absolute number of impressions and clicks. If the amount of impressions turns out much higher then with adsense, and the amount of clicks more or less the same, then you have your answer.

[midwestadsenseguy]

DUH! Thanks for the wake up call! You know it does appear that my impressions are roughly 4 times higher than they were under adsense. I'll need to do a bit more research to confirm but I think I may have found my answer to low Yahoo CTR ratios compared to Google.

[krod]

yes indeed they do, adsence counts each page load as a impression no matter how many ad units you have on it. Say if you 3 ad units using Adsence, and get 1,000 impression, it will report as 1,000 impressions. If you had YPN! running instead of adsence, and again got 1,000 impressions while having 3 ad blocks running it will report as 3,000 impressions. This is why i use YPN, and the CPM is much higher.