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         John K.-H. Quah

 

         Department of Economics          

           Oxford University

           Manor Road, OX1 3UL

        

            Email: john.quah@economics.ox.ac.uk          Phone: 01865-281291 (Economics Department); 01865-274986 (St Hugh’s College)

            Department webpage                                      College Webpage                                           

Office Hours                                                     Slides for Lectures

            Research interests:      monotone comparative statics, statistical decision theory, informativeness, supermodular games

                                                demand aggregation, general equilibrium theory

environmental economics  

           

Published (or soon-to-be published) Papers

·         Comparative Statics, Informativeness, and the Interval Dominance Order (with Bruno Strulovici), Econometrica, Vol. 77 (6), 1949-1992 (2009).

This paper identifies a new way to order functions, called the interval dominance order, that generalizes both the single crossing property and a standard condition used in statistical decision theory. This allows us to provide a unified treatment of the major theorems on monotone comparative statics with and without uncertainty, the comparison of signal informativeness, and a non-Bayesian theorem on the completeness of increasing decision rules. We illustrate the concept and results with various applications, including an application to optimal stopping time problems where the single crossing property is typically violated. 

Seminar slides and also slides on background material are available.  Additional related material is found in Comparative Statics with the Interval Dominance Order: Some Extensions (incomplete notes dated 9 December 2007; fuller version to be posted at a later date).   

·         The existence of equilibrium when excess demand obeys the weak axiom, Journal of Mathematical Economics, Vol. 44(3-4), 337-343 (2008)

 

This paper gives an elementary and instructive proof of equilibrium existence when the excess demand correspondence obeys the weak axiom of revealed preference.

 

·         The comparative statics of constrained optimization problems, Econometrica, Vol. 75, No. 2, 401-431 (2007)    

 

This paper extends of the methods of monotone comparative statics to deal with commonly-encountered comparative statics problems involving changes to constrain sets.  

See also  Additional notes on the comparative statics of constrained optimization problems, Working Paper, Nuffield College, Oxford, No. 2006-W09.   

 

·         A contribution to duality theory, applied to the measurement of risk aversion, (with Juan Enrique Martinez-Legaz) Economic Theory, Vol. 30, No. 2, 337-362 (2007)

 

We examine the precise connection between the curvature properties of an objective function and the ray-curvature properties of its dual. When the objective function is interpreted as a Bernoulli or cardinal utility function, our results characterize the relationship between an agent’s attitude towards income risks and her attitude towards risks in the underlying consumption space.

 

·         Weak Axiomatic Demand Theory, Economic Theory, Vol. 29, No. 3, 677-699 (2006) 

 

This paper identifies a class of complete but not necessarily transitive preferences which generate demand functions that obey the weak axiom of revealed preference and within which any function obeying the weak axiom can be rationalized. 

 

·         Homothetic or Cobb-Douglas behavior through aggregation,  Contributions to Theoretical Economics, Vol. 3, No. 1, Article 8 (2003)(with Gael Giraud)

We show how consumers' (heterogeneous) preferences in a market could be distributed in such a way that aggregate market demand takes on exact homothetic or Cobb-Douglas properties.

·         Market demand and comparative statics when goods are normal, Journal of Mathematical Economics, Vol.39, 317-333 (2003)

 

This paper gives a thorough exploration of the consequences arising from normal goods on market demand and on comparative statics in exchange, production and financial economies (the last with incomplete markets).

 

·         The law of demand and risk aversion, Econometrica, Vol. 71, 713-721 (2003)

 

I show that the law of demand can be characterized by a modified version of the Milleron-Mitjuschin-Polterovich condition.  The condition could be interpreted as a measure of differences in risk aversion when an agent encounters different lotteries over commodity bundles in commodity space.

·         The monotonicity of individual and market demand, Econometrica Vol. 68, No.4 (July 2000), 911-930

Early version:  The Monotonicity of Individual and Market Demand, Working Paper, Nuffield College, Oxford, No. 127, 1997.

In this paper, I study the law of demand in a market where the income distribution is independent of price.   I show that the law of demand  for market demand (market monotonicity) can arise through a range of conditions between two extremes known to guarantee market  monotonicity:  the  Milleron-Mitjuschin-Polterovich conditions on individual preferences and the Hildenbrand conditions on the income distribution.  

·         The law of demand when income is price dependent, Econometrica, Vol. 65, (November, 1997) 1421-1442

Early version:  Homothetic Preferences, Homothetic Transformation, and the Law of Demand in Exchange Economies,  Working Paper No. 93-210, Department of Economics, UC Berkeley.

I use a weaker form of the demand heterogeneity assumption employed by Grandmont (1992)  to guarantee the uniqueness and stability of the equilibrium price in exchange and production economies. 

            Survey

·         Law of Demand (with Michael Jerison). The New Palgrave Dictionary of Economics, Second Edition (2008).  Drop me an email if you would like a copy.

Selected working papers  

·         A Nonparametric Analysis of the Cournot Model   (with Andres Carvajal), Working Paper, Nuffield College, Oxford, No. 2009-W15. 

·         Discounting and Patience in Optimal Stopping and Control Problems (with Bruno Strulovici), Discussion Paper 1480, Northwestern University, Center for Mathematical Studies in Economics and Management Science (2009).

·         Emissions Trading and Profit Neutral Grandfathering (with Cameron Hepburn and Robert Ritz), Working Paper, Department of Economics, Oxford, No. 295.  Click here for the latest version of this paper; I also have some slides.  

·         The aggregate weak axiom in a financial economy through dominant substitution effects, Working Paper, Nuffield College, Oxford, No.2004-W18

·         The existence of equilibrium when excess demand obeys the weak axiom, Working Paper, Nuffield College, Oxford, No.2004-W7.  

·         The existence of perfect price indices in a market with heterogeneous agent 

·         Comparative statics and welfare theorems when goods are normal, Working Paper, Nuffield College, Oxford, No. 2001-W24.
Contains welfare theorems not published in Market demand and comparative statics when goods are normal, Journal of Mathematical Economics, Vol.39, 317-333 (2003).

·         Demand is heterogeneous in Grandmont's model, Working Paper, Nuffield College, Oxford, No. 2001-W12.

·         Comparative statics of the weak axiom, Working Paper, Nuffield College, Oxford, No. 2001-W3.  

·         The weak axiom and comparative statics, Working Paper, Nuffield College, Oxford, No. 1999-W15.

 

 

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