groups that are most successful in overcoming the free rider problems and securing more effort from their members are the groups that are the most successful in the political system. Note: an individual may be member of several different groups, including groups that oppose each other. For example, an auto worker might pay dues to a union that supports higher tariffs on car imports. But as a buyer of cars, he may pay dues to an auto club that opposes them. In his role as a producer he is a member of a pro-tariff group. In his role as a consumer, he is a member of an anti-tariff group. What matters most is the behavior of groups as groups, not the behavior of individual members. Political equilibrium Imagine a political system in which the laws change every week. One week we might have a tariff on auto imports; the next week it's gone; the week after that it's back again. That would describe a system with no political equilibrium. By contrast, equilibrium exists if the tariff tends to stay the same from week to week until there is a fundamental change in one of the parameters of the system. Goodman not only showed that the neoclassical approach realistically models stable political systems, he also identified what an equilibrium must look like. Continuing with the tariff example, the marginal effort the proponents are willing to make to secure a small increase in the tariff must equal the marginal effort the opponents are willing to make to oppose it. These efforts could be in the form of votes, campaign contributions, etc., and the kind of effort that is possible will differ from system to system. Any deviation from this condition means that the decision maker risks being replaced by a rival, who can gain an advantage by supporting the set of equilibrium policies over the deviation. Political prices The third innovation was to decompose the equilibrium condition. The marginal effort that producers are willing to make to secure a slightly higher tariff is the marginal economic benefit they expect multiplied times the effort they are willing to make per dollar of benefit. On the other side, the marginal effort consumers are willing to make to oppose the change is the marginal economic cost they expect to avoid multiplied times their effort per dollar of benefit. These effort-benefit ratios are the "political prices"