A new study from online ad network Chitika reveals that ranking high for popular queries between three and five words long should see both optimal traffic and conversions. 

Chitika looked at a sample of over 41 million impressions of search traffic coming into their network over a period of six days. 26% of all search traffic came from three-word searches, while two-term key phrases accounted for 19%, and four-term phrases accounted for 17% (one-word phrases accounted for 14%).

According to the official blog post on the study, "Any query beyond five words will see dramatically lower traffic, throwing into perspective just how fragmented traffic from long queries really is." 

Chitika also looked at the advertising click rate by word count to determine how visitors intent was refelcted in the quantity of words they searched for.

As you might guess, the highest ad click rates were for queries of 5,6, and 4 words respectively. That means that a longer search query is more likely to convert into revenue.