Recent evidence suggests that the use of prepaid cards is growing in the United States. The study of how prepaid cards fit into the existing payments market requires accurate data about the adoption of prepaid cards among consumers. This paper describes several experiments conducted by the Consumer Payments Research Center that compare the efficacy of various question forms regarding reported adoption rates. A primary focus is on the effect of "disaggregation" or asking about adoption of a number of prepaid card categories sequentially rather than asking about adoption of prepaid cards as a whole. We find strong evidence that increases in the number of categories yield higher adoption rates. Findings about the robustness of responses with changes in a few aspects of the question are also discussed.