Joseph Stiglitz is a professor of economics at Columbia University. He is a recipient of the Nobel Memorial Prize in Economic Sciences (2001) and the John Bates Clark Medal(1979). In addition to making numerous influential contributions to economics, Stiglitz has played a number of policy roles. He served in the Clinton Administration as the chair of the President's Council of Economic Advisors (1995 – 1997). At the World Bank, he served as Senior Vice President and Chief Economist (1997 – 2000). He was also a lead author for the Intergovernmental Panel on Climate Change.

Stiglitz has made numerous important contributions to economics and to economic modeling. Differing from the widely accepted paradigms of rational expectations/representative agent models or fixed price new Keynesian models, Stiglitz and his co-authors developed  models incorporating uncertainty,  imperfect information, incomplete markets, imperfect labor markets, imperfect capital markets, risk averse, credit constrained firms, in which concerns about bankruptcy often play an important role. Joseph Stiglitz's many contributions have transformed the way economists think about the working of markets. Many of these innovations have been incorporated into applied policy models in major institutions.

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http://nobelprize.org/nobel_prizes/economics/laureates/2001/stiglitz-lecture.pdf