1. A computer-implemented method to measure the quality of a candidate result set expanded from a set of seed items, the method comprising: receiving one or more seed items that represent members of a concept set for which a user wants to automatically generate additional members of the concept set; automatically identifying additional seeds based on the received one or more seed items; receiving one or more lists that include some items that are members of the concept set and other items that are not members of the concept set; receiving a candidate result set that expands the received seed items to include items suspected of being members of the concept set; determining a weight for each received list based on the received seeds, wherein the weight corresponds to an initial measure of the quality of the list; determining a similarity metric of each item in the received candidate result set with the received seed items based on which of the received lists contain each item and the determined list weights; determining a quality of the received candidate result set by combining the determined similarity metrics; and outputting the determined quality of the candidate result set, wherein the preceding steps are performed by at least one processor.