DoubleClick's Performics division yesterday introduced the Performics 50, an index of actively managed search engine marketing campaigns, and provided trending data for cost per keyword (CPK) from April 2004 through June 2005 in a Search Trend Report.

The campaigns studied are a mix of ecommerce and lead-based ones and constitute a representative sample of actively managed, direct-response oriented and mature but growing search campaigns. The Performics 50 therefore provides a stable benchmark against which trends in search marketing metrics can be analyzed, according to DoubleClick.

Among this initial study's major findings: Marketers expanded keyword use, resulting in increased "click volume," while keeping costs per keyword constant, reports AdAge, quoting Performics VP of marketing and product development Chris Henger. The number of keywords in active use more than doubled from June to June, click volume also increased, but costs were relatively flat.

With the release of the new index, Performics also proposed a new metric - cost per keyword (CPK) - to measure the quality of growth in a search marketing campaign. CPK addresses the monthly total cost of "ownership" for the average keyword and illustrates how actively consumers are searching and clicking for that keyword, as well as how marketers are valuing it, rather than how the most aggressive competitors are bidding on it.

DoubleClick says CPK is a scalable metric that can be used to evaluate the performance of individual keywords, groups of them or an entire portfolio.