Els Aerts, co-founder and managing partner of AGConsult found that only about 5% of her users were using search. And while some studies find higher numbers, everyone seems to agree that searchers are in the minority.
Wonder if they will mention later one can be both searchers and browsers; browsing most of the time when you don't exactly know what you're looking for; searching when you have a specific goal you're trying to achieve on a website.
Searching usually less successful (many websites have shit search functions) so people are less likely to use it as well. Might account for the 5% figure.