Search marketing firm Oneupweb released data showing that four-keyword queries were correlated with the highest conversion rates, compared with shorter and longer strings.
Over a roughly six-month period, average conversion rates for paid search ads appearing in response to those four-word queries were 36%. So what do we make of all this?
On the one hand you've got DoubleClick and Overture putting out research conducted with comScore that argues the vast majority of searches are at the one- and two-word category ("generic") level. The not-so-subtle implication here is: buy short phrases and don't neglect generic keywords.
However, in those studies, company names and trademark terms coverted better, but there's much less volume at those specific keyword levels. The Oneupweb data supports the latter idea.
In the same way that company names and trademarked terms may be a proxy for consumer buying intent, keyword query length seems to be as well (up to a point). So the Oneupweb research implication is: buy (SEM or SEO) those longer phrases.
Bottom line: buy short, buy long…buy everything.