Exotic Preferences for Macroeconomists

We provide a user's guide to exotic' preferences: nonlinear time aggregators, departures from expected utility, preferences over time with known and unknown probabilities, risk-sensitive and robust control, hyperbolic' discounting, and preferences over sets ( temptations'). We apply each to a number of classic problems in macroeconomics and finance, including consumption and saving, portfolio choice, asset pricing, and Pareto optimal allocations.

On optimality, endogeneous discounting and wealth accumulation

We endogenize the discount rate via a broad measure of wealth and provide empirical evidence that wealth the discount rate negatively. We demonstrate that the Pontryagin conditions require positive felicity for intuitive results, whereas the concavity of the Hamiltonian requires negative felicity for optimality. This dilemna also holds for the endogenizations of Obstfeld (1990) and followers. We solve the model with positive felicity and resolve when optimality is possible. We discuss the impact on technological change, savings and convergence which are more in line with empirics. Finally, we discuss time consistency of a planner who cannot predict his preferences.Endogenous time preference, Stability, Optimal growth, Recursive utility

Endogenous Discounting via Wealth, Twin-Peaks and the Role of Technology

The articles gives new answers to the following questions : One, what can be potential source of the twin-peaks of economi growth ? Two, why were some of the countries that were believed to belong to the group of low steady state countries (like Taiwan, South Korea, Japan, etc) able to reach a convergence path which led them to a high steady state ? We endogenize the time preference rate via a broad measure of wealth and provide empirical evidence that wealth affects the discount rate negatively. We provide sufficient conditions for multiplicity of equilibria and demonstrate how endogenous discounting via wealth leads to the twin-peaks of economic growth. We prove that improvements in technology can help avoid the Twin-peaks.Endogenous time preference, Recursive utility, Twin-peaks of economic growth

Endogenous discounting via wealth, Twin-Peaks and the role of technology

We endogenize the discount rate via wealth and provide evidence that wealth affects the discount rate negatively. We give a necessary and sufficient condition for endogenous discounting to lead to the Twin-Peaks of economic growth and show that improvements in technology help avoid them.endogenous discounting, Twin-Peaks of economic growth, multiple equilibria.

DISCOUNTING LONG RUN AVERAGE GROWTH IN STOCHASTIC DYNAMIC PROGRAMS

Finding solutions to the Bellman equation often relies on restrictive boundedness assumptions. In this paper we develop a method of proof that allows to dispense with the assumption that returns are bounded from above. In applications our assumptions only imply that long run average (expected) growth is sufficiently discounted, in sharp contrast with classical assumptions either absolutely bounding growth or bounding each period (instead of long run) maximum (instead of average) growth. We discuss our work in relation to the literature and provide several examples.Dynamic Programming; Weighted Norms; Contraction Mappings; Dominated Convergence; Non Additive Recursive Functions.

The First Conferences on the Theory of Economic Growth.

This paper presents the different conferences held around the subject of the theory of economic growth.ECONOMIC GROWTH ; ECONOMIC DEVELOPMENT ; ECONOMIC THEORY

Rethinking the Discount Factor in Reinforcement Learning: A Decision Theoretic Approach

Reinforcement learning (RL) agents have traditionally been tasked with maximizing the value function of a Markov decision process (MDP), either in continuous settings, with fixed discount factor $\gamma < 1$, or in episodic settings, with $\gamma = 1$. While this has proven effective for specific tasks with well-defined objectives (e.g., games), it has never been established that fixed discounting is suitable for general purpose use (e.g., as a model of human preferences). This paper characterizes rationality in sequential decision making using a set of seven axioms and arrives at a form of discounting that generalizes traditional fixed discounting. In particular, our framework admits a state-action dependent "discount" factor that is not constrained to be less than 1, so long as there is eventual long run discounting. Although this broadens the range of possible preference structures in continuous settings, we show that there exists a unique "optimizing MDP" with fixed $\gamma < 1$ whose optimal value function matches the true utility of the optimal policy, and we quantify the difference between value and utility for suboptimal policies. Our work can be seen as providing a normative justification for (a slight generalization of) Martha White's RL task formalism (2017) and other recent departures from the traditional RL, and is relevant to task specification in RL, inverse RL and preference-based RL.Comment: 8 pages + 1 page supplement. In proceedings of AAAI 2019. Slides, poster and bibtex available at https://silviupitis.com/#rethinking-the-discount-factor-in-reinforcement-learning-a-decision-theoretic-approac