In July 2009, Microsoft and Yahoo signed a 10-year deal following Microsoft's decision against buying Yahoo for $45 billion, as then-CEO Steve Ballmer had proposed back in 2008. The 2009 deal specified that Microsoft would power Yahoo search, and Yahoo become the ad sales force for Microsoft's premium properties.
The deal also included a clause that gave Yahoo the option to exit the partnership at the five-year mark, in February 2015, if Yahoo's 12-month average revenue-per-search (RPS) in the U.S. was less than a certain percentage of Google's estimated RPS.
Microsoft has been using its search partnership with Yahoo to grow its Web-search marketshare. But Microsoft, in the meantime, also has been integrating Bing into more and more of its products and services, as well as into Windows SKUs like Windows with Bing, in an attempt to increase usage of Bing indirectly.