A rising CPM doesn't mean your campaign is broken. CPM only measures cost per thousand impressions. What matters is CPA, your cost per acquisition. If CPM goes up but CPA stays flat, you're still profitable.
A lot of advertisers see CPM go up and panic. They assume something broke, start tweaking the campaign, and sometimes kill ads that were actually fine. But CPM is not the number to panic over. All it tells you is what it costs to reach 1,000 people. That can go up for a lot of reasons, and not all of them mean the ad is bad. The number that really matters is CPA. If CPM goes up but CPA stays steady, you're fine. If CPM goes up and CPA goes up too, then you need to pay attention. That's the difference. CPM is just information. CPA tells you whether the ad is still working. So before you touch a campaign because CPM jumped, look at the number that actually affects profit— that's CPA.
