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A Divide and Conquer Algorithm for Exploiting Policy Function Monotonicity


  • Grey Gordon

    () (Indiana University)

  • Shi Qiu

    () (Indiana University)


A divide and conquer algorithm for exploiting policy function monotonicity is proposed and analyzed. To solve a discrete problem with n states and n choices, the algorithm requires at most n log2(n) + 5n objective function evaluations. In contrast, existing methods for non-concave problems require n^2 evaluations in the worst case. For concave problems, the solution technique can be combined with a method exploiting concavity to reduce evaluations to 14n + 2 log2(n). A version of the algorithm exploiting monotonicity in two state variables allows for even more efficient solutions. The algorithm can also be efficiently employed in a common class of problems that do not have monotone policies, including problems with many state and choice variables. In the sovereign default model of Arellano (2008) and the real business cycle model, the algorithm reduces run times by an order of magnitude for moderate grid sizes and orders of magnitude for larger ones. Sufficient conditions for monotonicity are provided.

Suggested Citation

  • Grey Gordon & Shi Qiu, 2017. "A Divide and Conquer Algorithm for Exploiting Policy Function Monotonicity," CAEPR Working Papers 2017-006, Center for Applied Economics and Policy Research, Department of Economics, Indiana University Bloomington.
  • Handle: RePEc:inu:caeprp:2017006

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    References listed on IDEAS

    1. S. Rao Aiyagari, 1994. "Uninsured Idiosyncratic Risk and Aggregate Saving," The Quarterly Journal of Economics, Oxford University Press, vol. 109(3), pages 659-684.
    2. Carroll, Christopher D., 2006. "The method of endogenous gridpoints for solving dynamic stochastic optimization problems," Economics Letters, Elsevier, vol. 91(3), pages 312-320, June.
    3. Cristina Arellano, 2008. "Default Risk and Income Fluctuations in Emerging Economies," American Economic Review, American Economic Association, vol. 98(3), pages 690-712, June.
    4. Satyajit Chatterjee & Dean Corbae & Makoto Nakajima & José-Víctor Ríos-Rull, 2007. "A Quantitative Theory of Unsecured Consumer Credit with Risk of Default," Econometrica, Econometric Society, vol. 75(6), pages 1525-1589, November.
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    Cited by:

    1. Yongquan Cao & Grey Gordon, 2019. "A Practical Approach to Testing Calibration Strategies," Computational Economics, Springer;Society for Computational Economics, vol. 53(3), pages 1165-1182, March.
    2. Grey Gordon & Aaron Hedlund, 2017. "Accounting for the Rise in College Tuition," NBER Chapters, in: Education, Skills, and Technical Change: Implications for Future US GDP Growth, pages 357-394, National Bureau of Economic Research, Inc.
    3. Bommier, Antoine & Harenberg, Daniel & Le Grand, François, 2017. "Household Finance and the Value of Life," VfS Annual Conference 2017 (Vienna): Alternative Structures for Money and Banking 168189, Verein für Socialpolitik / German Economic Association.
    4. Yongquan Cao & Grey Gordon, 2016. "A Practical Approach to Testing Calibration Strategies," Caepr Working Papers 2016-004_updated Classifi, Center for Applied Economics and Policy Research, Economics Department, Indiana University Bloomington.
    5. Grey Gordon & Pablo Guerron-Quintana, 2019. "A Quantitative Theory of Hard and Soft Sovereign Defaults," 2019 Meeting Papers 412, Society for Economic Dynamics.

    More about this item


    Computation; Monotonicity; Grid Search; Sovereign Default;

    JEL classification:

    • C61 - Mathematical and Quantitative Methods - - Mathematical Methods; Programming Models; Mathematical and Simulation Modeling - - - Optimization Techniques; Programming Models; Dynamic Analysis
    • C63 - Mathematical and Quantitative Methods - - Mathematical Methods; Programming Models; Mathematical and Simulation Modeling - - - Computational Techniques
    • E32 - Macroeconomics and Monetary Economics - - Prices, Business Fluctuations, and Cycles - - - Business Fluctuations; Cycles
    • F34 - International Economics - - International Finance - - - International Lending and Debt Problems

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