The methodology for this research varies from earlier approaches in using a product-level, or “bottom-up”, approach, rather than a top-down, macro perspective. This makes it possible to base forecasts on what is most likely to change in the medicines market, e.g. the appearance of new products and the debut of new generics and biosimilars. OHE’s model for projecting NHS medicines expenditure was an important tool used by the Association of the British Pharmaceutical Industry to produce its forecast for discussion with the Department of Health about revisions to the PPRS.