Scores are calculated relative to national average

Editor-I agree with F Azeem Majeed and colleagues that a shift to a system of payments based on enumeration districts targets deprivation payments more sensitively and, from the point of view of implementation, stabilises total practice payments.1 2 Changing the areal unit on which the score is calculated (that is, enumeration district versus ward) does not, however, address the important underlying issue of change in social composition over time and its impact on general practitioners' workload and deprivation payments.

A fundamental reason for change in the underprivileged area score for a ward stems from the method of calculation, whereby the score is relative to the national average. Thus for a particular ward, even if the sociodemographic profile of its residents and its physical boundaries remain exactly the same from one census to the next, whether it qualifies for payment will depend on the position of that ward with respect to all other wards in Britain. Since the score is not linked to a baseline level of entitlement (such as the 1981 national means of the eight factors in the score), a practice that qualified for additional payments for its patients living in a deprived ward in 1981 might cease to qualify in 1991 not because the ward has, say, fewer lone parents or unemployed people but because a rise in the national percentages of these factors means that the ward scores lower on the underprivileged area index. Thus while the score takes into account the relative change in the distribution of deprivation between wards, it makes no allowance for the absolute change in the social factors that contribute to increasing workload in general practice.

Using the means and standard deviations of the eight factors in England and Wales in 1981 as a baseline, colleagues and I have shown that …