Before you block a Google-certified ad network, you should consider the following:
The ad auction process and the revenue share are the same for the Google Ads program as they are for Google-certified ad networks.
AdSense system will always show the highest paying ads, whether the ads come from Google Ads or an ad network.
If you block an ad network it might have a negative revenue impact because the blocked network won’t compete in the auction on your site, and therefore won’t drive up potential earnings for your ad space.
Revenue per thousand impressions (RPM)
RPM represents the estimated earnings you’d accrue for every 1000 impressions you receive. We do not recommend that you block ad networks based on RPM. Consider the following example:
Network B has the highest RPM and appears to be outperforming the other networks. However, this metric is based only on 14 impressions and doesn’t mean that you should expect the same revenue for the next 1000 or 10000 impressions.
The value of impressions varies widely so the RPM for a small number of impressions can be misleading.
Network C has the lowest RPM. However, blocking Network C because it has a low RPM might have a negative impact on revenue. Network C has a lower RPM because it’s winning the auctions of less valuable impressions.
AdSense system will always try to maximize the value of every impression in an auction. If you block Network C then another network with a lower-paying bid may win the auction.