Adaptive learning,endogenous uncertainty,and asymmetric dynamics

I present a simple model where forecasting confidence affects aggregate demand. It is shown that this model has similar stability properties, under statistical and evolutionary learning, as a model without a confidence affect. From this setup, I introduce “Expectational Business Cycles” where output fluctuates due to learning, heterogeneous forecasting models and random changes in the efficient forecasting model. Agents use one of two forecasting models to forecast future variables while heterogeneity is dictated via an evolutionary process. Increased uncertainty, due to a shock to the structure of the economy, may result in a sudden decrease in output. As agents learn the equilibrium, output slowly increases to its equilibrium value. Expectational business cycles tend to arrive faster, last longer and are more severe as agents possess less information.     

On the behavior of commodity prices when speculative storage is bounded

This paper investigates the implications of bounded speculative storage, storage bounded from below at zero and above at a capacity, on commodity prices. Binding capacity mirrors the non-negativity constraint on storage and leads to negative price spiking and higher volatility when the market is in deep contango, i.e. low current prices at high stock levels. With bounded storage there is no need to restrict storage to be costly to ensure a rational expectations equilibrium. This allows the model to cover a wide range of storage technologies, including free and productive storage. We also provide an alternative expression for speculative prices that highlights the key role of the storage boundaries. The competitive equilibrium price is the sum of discounted future probability weighted boundary prices. The boundary prices can be viewed as dividends on commodities in storage reflecting the realization of economic profits from storage.     

Switching bubbles: From Outside to Inside Bubbles

The United States has recently experienced two asset price bubbles: the Dot-Com and the Housing Bubbles. These bubbles had very different effects on investment and debt of manufacturing firms. In this paper I develop a framework to understand the differential effect of two types of rational bubbles. I distinguish between (i) Outside Bubbles, which I define as savers purchasing and selling costless assets not-attached to inputs of production and (ii) Inside Bubbles, which I define as savers buying an input of production (e.g., land or houses) only as a store of value. The model is an OLG economy with savers and entrepreneurs. Savers save to consume when they are old. Entrepreneurs can borrow to invest but they face a collateral constraint. In this environment, rational bubbles can emerge. I show that the size of an Inside Bubble is larger. I also find that when the economy switches from an Outside to an Inside Bubble, manufacturing (or non-housing) investment and debt is lower, consistent with the U.S. experience. Finally, I show that even though steady-state consumption is higher with an Outside Bubble, a social planner would prefer an Inside Bubble when the productivity of entrepreneurs is low.     

Mitigation of the Lucas critique with stochastic control methods

Lucas (In: Brunner, K., Meltzer, A.H. (Eds.), The Phillips Curve and the Labor Markets, Supplementary Series to the Journal of Monetary Economics, 1976, pp. 19–46) pointed out, that when optimization is performed on a deterministic macro model, the resulting policy may not reflect the true optimal solution. Private agents may react to announced policies and consequently model parameters will start to drift. The aim of this paper is to develop a methodology for deriving an optimal policy in the presence of rational expectations and parameter drift. This drift is captured by a stochastic optimization framework with time-varying parameters. The resulting optimal policy is capable of tracking changes in the parameters due to policy changes. A numerical example illustrates how the methodology provides a way to mitigate the effects of the Lucas critique.     

有效承接发达地区产业转移的金融政策选择——以广西为例

生产要素流动是区际产业转移的推动器,而此其中资金的流动和投资又是实现产业转移目标和提升产业转移绩效的关键。国内外的成功经验也表明,金融产业转移既是产业转移的重要领域,而且往往又是其中的先行领域,因此现阶段在承接区际产业转移的过程中,大力发展金融产业、积极构建有效的地方系统性的金融政策体系以及制定和实施有效的金融倾斜政策,无疑具有重要的现实意义。     

Introduction to economic theory of bubbles

This is an introduction to the special section on the economic theory of bubbles.     

Announcement

The paper focuses on Blaug's distinction between rational and historical reconstruction within the historiography of economics. Blaug's distinction is shown to be sterile and misleading and his definitions of no avail to clear thinking. Historical reconstruction (as defined by Blaug) is en empty box for reasons which are basically theoretical and not simply practical (as Blaug seems to hold). Moreover, Blaug's primary polemical target is Whig historiography and not rational reconstruction: the two concepts coincide only by means of an ad hoc definition. Blaug's criticism does not apply to other uses of the concept of rational reconstruction such as that proposed by Lakatos.     

农户偏好农村非正规金融的动因:理论模型与经验证据

在广大发展中国家及欠发达地区,农户参与正规金融市场的程度很低,尤其是贫困农户的参与度更低。已有的研究认为正规金融部门实施的信贷配给导致了上述现象的发生。而本文提出一个新的命题:农户偏好从非正规金融市场借款是出于成本收益的算计,是既定约束条件下的理性选择,越贫困的农户越偏好农村非正规金融市场。此外,还运用数理模型论证了该命题在理论上成立的可能性,并通过对相关调研资料的梳理及实地调研为该命题的成立提供了充分的经验证据。     

Sequentially complete markets remain incomplete

We show by means of an example that the result of Arrow [Arrow, K.J. (1953), Le rôle des valeurs boursières pour la répartition la meilleure des risques, Econométrie, 41–47, CNRS, Paris; translated as The role of securities in the optimal allocation of risk bearing, Review of Economic Studies, 31, 91–96] is problematic when there exist multiple equilibrium continuations to the initial-period component of an intertemporal equilibrium.     

Convergence for difference equations with vanishing time-dependence, with applications to adaptive learning

Summary. We provide conditions for local stability and instability of an equilibrium point in certain systems of nonautonomous nonstochastic difference equations. In the systems under study the influence of time is present through a positive scalar “gain” parameter which converges in the limit to zero. These systems have recently been used to study the dynamics of adaptive learning in economic models, and we provide two economic illustrations of the formal results. Received: October 7, 1997; revised version: February 8, 1999