Expectations and Economic Fluctuations

小行星9617501 本研究课题旨在探讨预期作为独立变量是否能够解释GDP或通货膨胀等经济总量变量的变动这一重要且尚未解决的课题。 宏观经济学中一个反复出现的主题是这样一种假设，即预期确实很重要，其重要性与货币、生产率和财政冲击处于同一数量级。 但是，标准的动态宏观经济模型假定了在解释经济波动方面发挥独立作用的可能性，而那些考虑到这种可能性的模型所作的假设并不吸引人。 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适应性学习下是稳定的。 将制定一个新的通货膨胀的税收模式，其中包括对赤字相对于国内生产总值的最大规模的财政限制（部分是受欧洲联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，该项目表明，即使存在低通胀均衡，也有可能陷入高通胀均衡。 然而，一项加强财政约束的政策可以促使经济向低通胀均衡移动。 第二条研究路线将分析一般动态多元线性模型中理性预期均衡（REE）的稳定性。 许多应用的宏观经济模型都可以用这个框架来近似。 该项目推导出REE在自适应学习下稳定的一般条件，并将结果应用于一系列示例。 第三条研究路线开发了一种表现增长周期的内生增长模型，即，商业信心和投资的自我实现变化所产生的增长率的均衡波动。 其基本机制基于（1）资本投入之间的互补性和（2）开发新设计的垄断竞争。 相关的工作包括：（1）与收益递增增长模型的统计时间序列含义的数据进行比较，（2）研究由遗传算法指导的资产需求建模对资产价格的含义，（3）开发新的技术工具，用于分析多重均衡存在时自适应学习的收敛性（4）研究异质期望的存在对趋同的影响。 ??

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. ??