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Optimal consumption in the stochastic Ramsey problem without boundedness constraints. (English) Zbl 1419.91497

Summary: This paper investigates optimal consumption in the stochastic Ramsey problem with the Cobb-Douglas production function. Contrary to prior studies, we allow for general consumption processes, without any a priori boundedness constraint. A nonstandard stochastic differential equation, with neither Lipschitz continuity nor linear growth, specifies the dynamics of the controlled state process. A mixture of probabilistic arguments are used to construct the state process, and establish its nonexplosiveness and strict positivity. This leads to the optimality of a feedback consumption process, defined in terms of the value function and the state process. Based on additional viscosity solutions techniques, we characterize the value function as the unique classical solution to a nonlinear elliptic equation, among an appropriate class of functions. This characterization involves a condition on the limiting behavior of the value function at the origin, which is the key to dealing with unbounded consumptions. Finally, relaxing the boundedness constraint is shown to increase, strictly, the expected utility at all wealth levels.

MSC:

91B62 Economic growth models
93E20 Optimal stochastic control
49L25 Viscosity solutions to Hamilton-Jacobi equations in optimal control and differential games

References:

[1] E. Bayraktar and Y.-J. Huang, {\it On the multidimensional controller-and-stopper games}, SIAM J. Control Optim., 51 (2013), pp. 1263-1297. · Zbl 1268.49045
[2] W. H. Fleming and H. M. Soner, {\it Controlled Markov Processes and Viscosity Solutions}, Stoch. Model. Appl. Probab. 25, 2nd ed., Springer, New York, 2006. · Zbl 1105.60005
[3] I. Karatzas and S. E. Shreve, {\it Brownian Motion and Stochastic Calculus}, Grad. Texts in Math. 113, 2nd ed., Springer, New York, 1991. · Zbl 0734.60060
[4] S. Karlin and H. M. Taylor, {\it A Second Course in Stochastic Processes}, Academic Press, New York, 1981. · Zbl 0469.60001
[5] N. V. Krylov, {\it Controlled Diffusion Processes}, Stoch. Model. Appl. Prob. 14, Springer, Berlin, 2009. · Zbl 1171.93004
[6] C. Liu, {\it Optimal consumption of the stochastic Ramsey problem for non-Lipschitz diffusion}, J. Inequal. Appl., 2014 (2014), 391. · Zbl 1335.49030
[7] R. Merton, {\it An asymptotic theory of growth under uncertainty}, Rev. Econ. Stud., 42 (1975), pp. 375-393. · Zbl 0355.90006
[8] H. Morimoto, {\it Optimal consumption models in economic growth}, J. Math. Anal. Appl., 337 (2008), pp. 480-492. · Zbl 1141.91611
[9] H. Morimoto, {\it Stochastic Control and Mathematical Modeling}, Encyclopedia Math. Appl. 131, Cambridge University Press, Cambridge, 2010. · Zbl 1242.93003
[10] H. Morimoto and X. Y. Zhou, {\it Optimal consumption in a growth model with the Cobb-Douglas production function}, SIAM J. Control Optim., 47 (2009), pp. 2991-3006. · Zbl 1176.49033
[11] S. Nakao, {\it On the pathwise uniqueness of solutions of one-dimensional stochastic differential equations}, Osaka J. Math., 9 (1972), pp. 513-518. · Zbl 0255.60039
[12] H. Pham, {\it Continuous-Time Stochastic Control and Optimization with Financial Applications}, Stoch. Model. Appl. Probab. 61, Springer, Berlin, 2009. · Zbl 1165.93039
[13] F. P. Ramsey, {\it A mathematical theory of saving}, Econom. J., 38 (1928), pp. 543-559.
[14] T. Yamada, {\it On a comparison theorem for solutions of stochastic differential equations and its applications}, J. Math. Kyoto Univ., 13 (1973), pp. 497-512. · Zbl 0277.60047
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