Google's looking at a new option that would be based on conversions.

If you're an old-school AdWords advertiser, you may remember that you originally set bids based on ad impressions (cost-per-impression, or CPM). Later, AdWords transitioned to a new model where bids were set based on ad clicks (cost-per-click, or CPC). Now, as technology has become even more advanced, we’re seeing the next phase of search engine advertising.

What if we told you that you could bid for ads simply based on conversions? (A conversion is a goal set by an advertiser, such as a website visitor purchasing a product or filling out a form.) With Conversion Optimizer, Google does all the heavy lifting and complicated analysis, letting you bid simply based on how much a conversion is worth to your business (cost-per-acquisition, or CPA). By using Conversion Optimizer, advertisers are not only seeing an increase in profits but have more time to devote to the rest of their business.

Official Google Blog: Leave the math to us: Advertisers increase their profits using Conversion Optimizer