Editing Cost per action (section)

==Effective cost per action==
A related term, [[effective cost per action]] (eCPA, eCPX),<ref>{{Cite book |last1=Zhou |first1=Tian |last2=He |first2=Hao |last3=Pan |first3=Shengjun |last4=Karlsson |first4=Niklas |last5=Shetty |first5=Bharatbhushan |last6=Kitts |first6=Brendan |last7=Gligorijevic |first7=Djordje |last8=Gultekin |first8=San |last9=Mao |first9=Tingyu |last10=Pan |first10=Junwei |last11=Zhang |first11=Jianlong |last12=Flores |first12=Aaron |chapter=An Efficient Deep Distribution Network for Bid Shading in First-Price Auctions |date=2021-08-14 |title=Proceedings of the 27th ACM SIGKDD Conference on Knowledge Discovery & Data Mining |chapter-url=https://dl.acm.org/doi/abs/10.1145/3447548.3467167 |series=KDD '21 |location=New York, NY, USA |publisher=Association for Computing Machinery |pages=3996–4004 |doi=10.1145/3447548.3467167 |isbn=978-1-4503-8332-5|arxiv=2107.06650 }}</ref><ref>{{Citation |last1=He |first1=Hao |title=Mid-flight Forecasting for CPA Lines in Online Advertising |date=2021-07-15 |arxiv=2107.07494 |last2=Zhou |first2=Tian |last3=Ren |first3=Lihua |last4=Karlsson |first4=Niklas |last5=Flores |first5=Aaron}}</ref> is used to measure the effectiveness of advertising inventory purchased (by the advertiser) via a [[cost per click]], [[cost per impression]], or [[cost per thousand]] basis.

In other words, the eCPA tells the advertiser what they would have paid if they had purchased the advertising inventory on a cost per action basis (instead of a cost per click, cost per impression, or cost per mille/thousand basis).

If the advertiser is purchasing inventory with a CPA ''target'', instead of paying per action at a fixed rate, the goal of the effective CPA (eCPA) should always be below the maximum CPA.