A report from emarketer today - Search Query Keyword Insight - details the results of some research over the past year to analyze which types of search phrases yield the highest conversion rates. Not surprisingly, a direct correlation was found between the number of words in the phrase (query) and the liklihood of purchase - as the number of terms in the query rises, so too do the conversion rates. Most searchers are now using 3-4 words, with 2 and 5 word phrases being somewhat popular, while 1 and 6+ phrases are less common.

The report also gives some insight into how users search - noting that very few searchers will attempt any of the so-called advanced operators, including quotes, link commands, allin or intitle, etc.