This paper considers the strengths and weaknesses of using spending market research companies information (that records very detailed spending down to the bar code level from a panel of households) when collecting comprehensive panel expenditure data, and the implications of survey mode on the recorded data. The authors conduct an in-depth examination of scanner data from one company, Taylor Nelson Sofres (TNS), on grocery purchases over a five-year period. They assesses how far the ongoing demands of participation inherent in this kind of survey lead to 'fatigue’ in respondents' recording of their spending and compare the demographic representativeness of the data to the well established Expenditure and Food Survey (EFS), constructing weights for the TNS that account for observed demographic differences. They also look at demographic transitions, comparing the panel aspect of the TNS to the British Household Panel Study (BHPS). The paper examines in detail the expenditure data in the TNS and EFS surveys and discuss the implications of this method of data collection for survey attrition. Broadly, the paper suggests that problems of fatigue and attrition may not be so severe as may be expected, though there are some differences in expenditure levels (and to some extent patterns of spending) that cannot be attributed to demographic or time differences in the two surveys alone and may be suggestive of survey mode effects. Demographic transitions appear to occur less frequently than we might expect which may limit the usefulness of the panel aspect of the data for some applications.