In a recent Note in this Journal, Johnston and Pattie (2000) contend that they have discovered an ecological fallacy in the behaviour of the six-item scale developed by Heath et al. to measure the ‘left–right’ political value dimension. Using data from the first six waves of the British Household Panel Study (BHPS), they show that, while there is remarkable over-time stability in the factor structure of these questions at the aggregate level, when the consistency of individual responses to each item is considered, a very different picture emerges; around 50 per cent of the sample fail to select the same response alternative on successive waves and a third of respondents select a response alternative on the opposite side of the agree/disagree scale from one time to the next. Correlations between the same items over time of around 0.4, they argue, bear out a picture of massive longitudinal instability at the individual level.