My website has the adsense code of two publishers. One is based in North America (USD) and the other in North Africa (EURO). Obviously they are not displayed simultaneously. For each impression, one code is randomly selected to show. we have been monitoring the RPM for the two accounts and we noticed that the earning for the US account are on average 40% higher. Is this normal? I am not sure how the VAT works but the difference is much higher than the 20% VAT.
The codes are displayed on the same pages, randomly, and not based on the location of the visitors... We have been monitoring for several days and the number of impressions are high enough for the average to be significant.