The figures relating to "spend on statins per patient" were provided to the BBC by the NHS Prescription Prescribing Authority. They cover the period Oct 06 - Sept 07. "Patients" include all people in the PCT area - not just those using statins.
The NHS calculates the potential annual saving on each PCT's statins bill. It looks at what proportion of prescriptions in each area is for "low cost" statins. If that figure is less than 77%, the NHS believes there is a potential saving to be made. The figure of 77% is chosen because this is what is achieved by the best performing 25% of PCTs. These estimated figures are based on data collected in the 2nd quarter of 2007/8.