Back to the glossary
CPM (Cost per mille)
The cost of a thousand impressions: the price of being shown, rather than the price of a result.
The base rate of paid social. It moves with the audience you asked for, the competition for that audience, and the time of year. The same campaign costs noticeably more in the weeks before Christmas than it does in February.
A rising CPM on a campaign nobody has touched usually means creative fatigue rather than a market shift. The auction charges more to keep showing an ad the audience has started to ignore.
On its own it says nothing about whether the money worked. It is a diagnostic for why a cost per result moved, not a result in itself.