As you may know, Microsoft and Yahoo have a “search alliance” which sees Microsoft powering Yahoo’s organic search results, as well as migrating Yahoo Search Marketing to Microsoft’s adCenter.

The organic transition has already happened worldwide, and the ad platform transition is still in the process. In fact, the companies just announced that it’s rolling out in the UK, Ireland and France.

In a post on Yahoo’s Advertising Solutions blog, Yahoo is pointing to four recent studies from Efficient Frontier, Marin Software, Rimm-Kaufman Group (RKG) and Ignition One, and pulling out some points made in these about the momentum of the search alliance’s paid side:

• “On a year over year basis, our customers realized a 44% higher click volume combined [on Yahoo! Search and Bing]” — Marin U.S. Online Advertising Report, October — December 2011
• “Yahoo! Search and Bing clicks are 14% more valuable than Google, while also having 9% more ROI than Google” — Efficient Frontier, Global Q4 2011 Digital Marketing Performance Report
• “ROAS on Yahoo! Search and Bing was up 9.8% Y/Y in Q4…” — RKG Digital Marketing Report, Q4 2011
• “Yahoo! Search and Bing spend growth topped Google in the last two months of the year” — Ignition One Global Online Advertising Report, Q4 2011

According to Microsoft, the transition should be complete in the previously mentioned European countries by the end of April.