1. A computer-implemented method comprising: receiving information identifying a first search query through a communication interface; receiving information identifying a second search query through the communication interface, wherein the first search query differs from the second search query; accessing information characterizing prior input of the identified search queries by clients into a search engine, the information characterizing the prior input being stored in computer memory; determining, from the accessed information characterizing the prior input, a query volume for the first search query during a first period of time for which prior input of the identified search queries is characterized by the information stored in the computer memory; determining, from the accessed information characterizing the prior input, a query volume for the second search query during a second period of time for which prior input of the identified search queries is characterized by the information stored in the computer memory; generating, using one or more processors, a first representation of the query volume for the first search query relative to two or more variables and a second representation of the query volume for the second search query relative to the two or more variables; processing, using the one or more processors, the first representation and the second representation to generate a first set of wavelets representing the first representation and a second set of wavelets representing the second representation; identifying, using the one or more processors, a first subset of wavelets having high magnitude coefficients for the first set of wavelets and a second subset of wavelets having high magnitude coefficients for the second set of wavelets; generating, using the one or more processors, a first signature for the first representation based on the first subset of wavelets and a second signature for the second representation based on the second subset of wavelets; and determining, using the one or more processors, whether the first search query and the second search query are related by comparing the first signature to the second signature.