Some of you have heard the term "eCPM decay." Let's first understand what it means. If you are a publisher, CPM is the revenue you are getting for 1,000 impressions. If an advertiser is paying you a CPM of $5 and you show your users 1,000 impressions of that ad, you will receive $5. The advertising world is slightly more complex, however; most of the advertisers are actually paying CPI -- in other words, they are paying for installs. This means that unless the user clicks on an ad and installs the app, the publisher doesn't receive any revenue. What eCPM decay means is that if you take a certain user and show him more ads, he is not necessarily going to install more apps, so you wouldn't receive more money as a result. Simple Example of eCPM Decay Let's think of this scenario: You have a single user in a given day He wants to get 1 life for free, so he watches a video -- you as a publisher don't get paid for that