According to Efficient Frontier's lates data, the Yahoo-Bing paid search partnership has produced a couple positive trends for advertisers.
The company says that as traffic quality improved, RPCs rose throughout the Yahoo-Bing transition. At the start of the transition RPCs on the combined platform were 20% worse than Google but by the end of Dec the revenue-per-click (RPC) on Google and Yahoo-Bing were identical.
The company also says advertisers on Yahoo-Bing notice the higher ROI opportunities than expected, and given that the ROI on Yahoo traffic was 20-25% worse than Google's and Bing's ROI was 25% better, the weighted ROI of the combined traffic should have been 5-7% worse than Google. However, it's about the same as Google now. Thus, Bing has done well on this front. However, it remains to be seen if it can expand its click share while keeping its RPCs high.