Expectations and Economic Fluctuations

9617501埃文斯这个项目解决了一个重要但尚未解决的问题，即预期是否有能力作为独立变量来解释国内生产总值或通胀等总体经济变量的波动。宏观经济学中反复出现的一个主题是这样一种假设：预期确实很重要，它们的重要性与货币、生产率和财政冲击具有相同的量级。但标准的动态宏观经济模型排除了在解释经济波动方面发挥独立作用的可能性，而那些允许这种可能性的模型做出了不具吸引力的假设。该项目构建了期望具有独立作用的模型，并且这些解决方案在自适应学习下是稳定的。将开发一个新版本的通胀率铸币税模型，其中包括对赤字相对于GDP的最大规模进行财政限制(部分受到欧盟货币联盟条件的启发)。当在自适应学习下研究该模型时，出现了许多新的特征。例如，这个项目表明，即使存在低通胀均衡，也有可能陷入高通胀均衡。然而，收紧财政限制的政策可以诱导经济走向低通胀均衡。第二条线将分析一般动态多变量线性模型中理性预期均衡(REE)的稳定性。许多实用的宏观经济模型都可以用这个框架来近似。该项目推导了稀土元素在自适应学习下稳定的一般条件，并将结果应用于一系列例子。第三类研究开发了内生增长模型的一个版本，该模型展示了增长周期，即商业信心和投资的自我实现转变所产生的增长率的均衡波动。其基本机制是基于(1)资本投入之间的互补性和(2)新设计开发中的垄断竞争。相关工作包括：(1)与收益递增增长模型的统计时间序列影响的数据进行比较；(2)在遗传算法的指导下对资产需求建模对资产价格的影响进行调查；(3)开发新的技术工具，用于分析在存在多个均衡的情况下自适应学习的收敛；(4)研究异质预期的存在对收敛的影响。?？

9617501 Evans This project addresses the important and as yet unresolved issue whether expectations have power as independent variables to explain fluctuations in aggregate economic variables such as GDP or inflation. A recurrent theme in macroeconomics has been the hypothesis that expectations do matter, and that their importance is of the same order of magnitude as monetary, productivity and fiscal shocks. But standard dynamic macroeconomic models assume away the possibility of an independent role in explaining economic fluctuations and those models which allow for this possibility make unappealing assumptions. This project constructs models in which expectations have an independent role and in which such solutions are stable under adaptive learning. A new version of the seignorage model of inflation will be developed which includes a fiscal restriction (inspired in part by the European Union conditions for Monetary Union) on the maximum size of the deficit relative to GDP. When this model is studied under adaptive learning a number of novel features emerge. For example, this project shows that it my be possible to become trapped in a high inflation equilibrium, even when a low inflation equilibrium exists. However, a policy which tightens the fiscal restriction can induce the economy to move to the low inflation equilibrium. A second line of research will analyze the stability of the rational expectations equilibrium (REE) in a general dynamic multivariate linear model. Many applied macroeconomic models can be approximated by this framework. The project derives general conditions for REE to be stable under adaptive learning and apply the results to a range of examples. A third line of research develops a version of an endogenous growth model which exhibits growth cycles, i.e., equilibrium fluctuations in growth rates generated by self fulfilling shifts in business confidence and investment. The underlying mechanisms are based on (1) complementarities between capital inputs and (2) monopolistic competition in the development of new designs. Related work includes (1) a comparison to the data of the statistical time series implications of the increasing returns growth model, (2) investigation of the implications for asset prices of modeling asset demands as guided by a genetic algorithm,, (3) the development of new technical tools for analyzing the convergence of adaptive learning in the presence of multiple equilibria (4) study of the implications for convergence of the presence of heterogeneous expectations. ??