Can the average CPM per line exceed the “Maximum average CPM per line”?
- The planned budget has not been spent in its entirety yet (under the “Budget” and “Average CPM” strategies) or all the planned impressions have not been served yet (under the “Minimum CPM” strategy).
You selected the “Budget” strategy. The planned budget is 100 000 RUB, maximum average CPM — 100 RUB. The used budget (at the current moment) is 3 000 RUB, the number of paid impressions is 25,000 RUB. Actual average CPM (at the current moment) is 3 000/25 = 120 RUB.
This is because the actual CPM in this scenario is only calculated for part of the line period, whereas the limit applies to the entire period.
- During the course of a line, the planned budget or number of impressions was adjusted down or the end date was pushed up. Before that change was made, the average CPM exceeded the limit (see situation #1). As a result, the algorithm can't keep the CPM under the stated maximum in the short time that remains.
You chose the “Budget” strategy. The planned budget is 100 000 RUB, maximum average CPM — 100 RUB. The used budget (at the current moment) is 3,000 RUB, the number of paid impressions is 25,000 RUB. Actual average CPM (at the current moment) is 3,000/25 = 120 RUB. The planned budget was increased by 6,100 RUB. The rest of the budget (6,100 — 3,000 = 3,100 RUB) was used to pay for 31,000 impressions (3,100/100 = 31,000), the 100 RUB CPM restriction is observed. However, because major changes were made to the plan during the course of the line, the final CPM will still exceed the maximum average CPM.
- The maximum average CPM was lowered significantly over the course of the line. To stay within the new limit, bids decreased significantly and impressions were served at a slower rate because competitors did not allow impressions to be purchased at such a low rate at auction. As a result, the number of impressions served is so low that the average CPM will exceed the (recently lowered) maximum CPM.
“Maximum CPM per line” is 120 RUB. 90% of line is shown with actual average CPM, that is 100 RUB. The limit is lowered to 50 RUB. Even if all the remaining impressions cost one rouble, the average CPM in this case is 0.9*100+0.1*1=90.1 RUB.