hat means Microsoft has to do something different than just build new software that improves on the cost per click advertising model. And moving to a CPA model isn’t enough - Google and others are already experimenting with that. So instead, Microsoft is taking the CPA model, which lowers risk to advertisers, and combining it with a straightforward payback mechanism to users. This only applies to ecommerce-related searches for now. But frankly that is all that matters. Only about a third of searches are commerce-related, but those searches generate 80% of search revenue. Get the commerce searches and you’ve got the revenue. And here’s another interesting statistic - 68% of online purchases begin at a search engine or shopping comparison site. Only about 30% are from direct navigation to the ecommerce site itself.