CPM

CPM is the price of reach. It rises when you choose a small, popular audience or when many advertisers bid on the same people, such as around the holidays.

For campaigns at the top of the funnel CPM is a sensible yardstick. For sales campaigns it says less: expensive reach that converts well can beat cheap reach that does nothing.

A suddenly rising CPM at a stable budget is often a sign that your creative is worn out or your audience has become too narrow.