Using scanner technology to collect expenditure data

In terms of collecting panel expenditure data, there are trade-offs between the demands imposed on respondents and the detail and coverage of data collected. Comprehensive spending data tend to be cross-sectional whilst panel studies include only limited, aggregated expenditure questions. Recently, economists have begun to use detailed, bar-code-level spending data from household panels collected by market research companies. However, there has not been a detailed assessment of the strengths and weaknesses of this collection method or its implications for the recorded data. This paper seeks to fill this gap by providing an in-depth examination of data from one company, Taylor Nelson Sofres (TNS), recording grocery purchases over five years. We assess how far the ongoing demands of participation lead to 'fatigue' in respondents' recording of their spending and the implications for household attrition, and we provide a detailed comparison of the expenditure data collected by TNS and the well-established Expenditure and Food Survey (EFS). Broadly, we suggest that problems of fatigue and attrition may not be particularly severe, though there are differences in expenditures that cannot be attributed to demographic or time effects and may be suggestive of survey mode effects.