process, externalities, public goods, preference development and institutional structures." The traditional socialist solution of public enterprise combined with centrally planned allocation was found equally lacking. In conclusion they argued that in clarifying the reasons why traditional models were deficient they had cleared a path that suggested probable directions for an alternative paradigm. The significant social and ecological inefficiencies of private enterprise market economies, public enterprise centrally planned economies, and related variants, necessitated both the re-organization of production and consumption institutions and the search for compatible "allocative mechanisms that allow informed individual rationality to be fully consistent with social rationality." Their next step, the formulation of a relatively detailed "full" vision of an economy based upon participatory democratic planning was their attempt to provide an answer to this challenge. Participatory economics In 1991, as the Soviet bloc crumbled and capitalism emerged triumphant Albert and Hahnel published "The Political Economy of Participatory Economics", a model of an economy based upon allocation by participatory democracy within an integrated framework of nested production and consumption councils that was proposed as an alternative to contemporary capitalism, centralized state socialism and market socialism. In ensuing years Hahnel and Albert fleshed out the gaps in their vision, discussed possible complementary political and cultural institutions, and replied to many of their critics. Ecological economics Throughout much of this time Hahnel had been teaching advanced courses in ecological economics at American University. His ecological economic vision seeks to incorporate the ecological and social costs entailed in production, consumption, and distribution in the price signals for each good. Because of the widely recognized difficulties of quantifying ecological and social costs, Hahnel emphasized the necessity of utilizing qualitative data in addition to quantitative data to ensure accurate price signals. Qualitative data can best be elucidated through the mechanisms of an inclusive and participatory democratic informational framework. In terms of the current day ecological problems Hahnel acknowledges that green and pollution taxes are likely to be more effective than alternative schemes such as the marketization of natural resources using permit systems or regulatory "command and control" methods. An optimally efficient green tax requires taxing polluters an amount equal to external costs. Corporations can be expected to try to pass the extra costs on to consumers by raising prices; however, Hahnel notes that "part of the reason pollution taxes improve efficiency in a market economy is that they discourage consumption of goods whose