Need, demand, supply in health care: working definitions, and their implications for defining access.

Effective policymaking in health care systems begins with a clear typology of the terminology - need, demand, supply and access to care - and their interrelationships. However, the terms are contested and their meaning is rarely stated explicitly. This paper offers working definitions of need, demand and supply. We draw on the international literature and use a Venn diagram to explain the terms. We then define access to care, reviewing alternative and competing definitions from the literature. We conclude by discussing potential applications of our conceptual framework to help to understand the interrelationships and trade-offs between need, demand, supply and access in health care.