Several groups must work hand in hand to educate and inform farmers about seed of improved varieties. When campaigns to introduce new varieties or other technology to farmers seem, to be less successful than anticipated, the leaders of a campaign usually blame the resistance of farmers. Governments encourage the use of seed of improved varieties to increase production and improve diets, to reduce imports of food, to earn foreign exchange through agricultural exports, or to raise the incomes of farmers. Promoting the adoption of new varieties involves informing, persuading, and teaching more people than just the farmers. To influence national agricultural productivity, good seed of superior varieties must be purchased and used by thousands of farmers, so seed marketing focuses upon the user rather than the product. The promotional work of seed enterprises and marketing groups that sell varieties developed by public research groups should complement the latter's research and educational activities.