Does Capitalization Matter in Web Search?

We investigate the capitalization features of queries submitted to Web search engines and the relation between capitalization information, either as received from users or as hypothesized based on Web statistics, and search relevance. We observe that users tend to lowercase words in their queries significantly more often than as predicted from Web data. More importantly, we determine that document relevance is strongly correlated with the matching in capitalization between the instances of query tokens in the target document and the tokens of the truecased form of the query as obtained by using Web n-gram data.