Recent policy changes allow merchants to influence consumers' choice of payment instruments by offering price discounts and other incentives. This report describes lessons learned from using consumer survey responses to assess whether merchants tried to influence buyers' choice of payment method. To measure the effects of these recent policy changes, we included questions about merchant steering in pilot versions of a new diary survey of U.S. consumers. Our findings are inconclusive because some respondents interpreted the questions differently from the way we intended. This report aims to explain why the diary survey failed to deliver the desired results, and to suggest better ways to use surveys to evaluate the effects of policy changes in the future.