Motivated misreporting occurs when respondents give incorrect responses to questions to shorten a survey interview. Previous research has shown that motivated misreporting occurs across many modes, topics and countries. Those studies have often relied on questions about purchases to elicit the motivated misreporting effect. This paper tests for the presence of measurement error in the U. S. Consumer Expenditure Survey. The data from this survey inform the calculation of the Consumer Price Index in the US, among other uses. Using a novel approach involving a parallel web survey and multiple imputation, we estimate the size of the misreporting effect in the first wave of the Consumer Expenditure Survey without experimentally manipulating questions in the survey itself. In a second paper, we test whether respondents change their responses over waves to reduce the burden of the survey. Results suggest that respondents underreport purchases in the first wave of the survey, but the effect does not grow over waves. These results will be relevant to all survey researchers who use filter questions.