In theory, Iranian agricultural policy is intended to support farmers and encourage the production of strategically important crops. The policy is twofold: first, to purchase certain crops at guaranteed prices and second, to encourage the production of specific crops through farm subsidies. The policy of purchasing agricultural crops from farmers at guaranteed prices was put in place in the 1989 crop year. On average, the guaranteed prices increased at the rate of inflation over the past 15 years. Individual subsidy levels for major crops, however, vary annually.