"participatory planning is not central planning", stating "The procedures are completely different and the incentives are completely different. And one of the important ways in which it is different from central planning is that it is incentive compatible, that is, actors have an incentive to report truthfully rather than an incentive to misrepresent their capabilities or preferences." Unlike historical examples of central planning, the parecon proposal advocates the use and adjustment of price information reflecting marginal social opportunity costs and benefits as integral elements of the planning process. Hahnel has argued emphatically against Milton Friedman's a priori tendency to deny the possibility of alternatives: Friedman assumes away the best solution for coordinating economic activities. He simply asserts "there are only two ways of coordinating the economic activities of millions—central direction involving the use of coercion—and voluntary cooperation, the technique of the marketplace." [...] a participatory economy can permit all to partake in economic decision making in proportion to the degree they are affected by outcomes. Since a participatory system uses a system of participatory planning instead of markets to coordinate economic activities, Friedman would have us believe that participatory planning must fall into the category of "central direction involving the use of coercion." Albert and Hahnel have voiced detailed critiques of centrally-planned economies in theory and practice, but are also highly-critical of capitalism. Hahnel claims "the truth is capitalism aggravates prejudice, is the most inequitable economy ever devised, is grossly inefficient—even if highly energetic—and is incompatible with both economic and political democracy. In the present era of free-market triumphalism it is useful to organize a sober evaluation of capitalism responding to Friedman's claims one by one." Critique of markets Mainstream economists largely acknowledge the problem of externalities but believe they can be addressed either through Coasian bargaining or the use of Pigovian taxes—extra taxes on goods that have externalities. According to economic theory, if Pigovian taxes are set so that the after-tax cost of the goods is equal to the social cost of the goods, the direct cost of production plus cost of externalities, then quantities produced will tend toward a socially optimal level. Hahnel observes, "more and more economists outside the mainstream are challenging this assumption, and a growing number of skeptics now dare to suggest that externalities are prevalent, and often substantial". Or, as E.K. Hunt put it: externalities are the rule rather than the exception, and therefore