Yahoo increased it share of US search-ad revenue to 19.3 in the first quarter of 2009, up 1 percent from the year ago period, according to search marketing firm Efficient Frontier. From the year ago period, Google dropped .9 percent to 72.3 percent and Microsoft dropped 1 percent to 3.5 percent. Google had a click-through rate (CTR) of 2.38 and cost per click (CPC) of 54 cents in the first quarter of 2009, Yahoo CTR of 1.16 and CPC of 42 cents, and Microsoft CTR of 2.19 and CPC of 52 cents. The data is based a subset of Efficient Frontier clients and is comprised of over 84 billion impressions and 785 million clicks.