EDITOR,—Measures based on entitlement to free prescriptions because of low income are attractive as indices of deprivation, but there are inherent drawbacks to an index based on the number of prescriptions rather than of people receiving (or entitled to) them.

Firstly, as David C E F Lloyd and colleagues comment about their proposed low income scheme index, the “deprivation score is calculable but is affected by the individual habits of prescribers.”1 The effect is simply illustrated if different relative prescribing rates (1–3) are used for a population …