Provision for the Common Agricultural Policy (CAP) was integral to the agreements that established the European Union (EU) and the CAP has been among the most important EU policies administered and funded in common. Revisions or " reforms " of the CAP have been numerous,in response to dramatic changes in agricultural realities and circumstances since the 1960s. This report contends that the continuing need for revision results significantly from the interventionist nature of the CAP, which manages agricultural prices, precluding automatic market-directed adjustments of production and consumption to changing circumstances. Strong vested interests will continue to limit reforms, allowing revisions only when the immediate political costs of not reforming equal or exceed the costs of reform.