Macroeconomics and Inequality

美国经济是世界上最富有的经济体之一，无论是按人均财富还是按人均产出计算，但它也是一个贫富对比非常鲜明的经济体。这种不平等的根源是什么？经济学家和政策制定者是否应该对此感到担忧？这也许是成为世界上最富有的人的一个自然的，甚至是必要的方面，或者它反映了一个可以通过经济政策解决的失败？即使不平等本身不是一个令人担忧的原因，它会影响总体经济活动吗？ 虽然已经取得了很大的进展，学院派经济学家还没有能够解决上述问题，在数量上令人满意的方式。首先，很少有自然实验可以直接使用纯经验方法来讨论这些问题。其次，充分的经济理论基本上缺失。这项研究涉及第二点：它旨在继续发展对不平等的根源及其与宏观经济的相互关系进行定量研究所需的理论和数值工具。特别是，本项目是本研究员与合作者早期项目（NSF资助#9807760）的延续。这项工作沿着几条战线进行，但共同的主题是发展和应用宏观经济学和不平等的定量理论研究中普遍使用的方法。 核心问题是相当基本的问题：是什么决定了不同的人如何储蓄，包括人力资本和物质资本？技术变革如何影响工资不平等？经济政策如何影响不平等，以及它如何受到不平等的影响？该项目有具体的应用，但大部分工作是在相当广泛的适用性问题上。这些子项目如下：不平等的根源：A。储蓄：为什么家庭储蓄倾向如此不同？这个项目延续了早期关于初始财富差异和劳动力市场运气的作用的研究，但也更进一步：是什么决定了“贴现因素”？这里的方法是心理学和经济学的方法之一;心理学文献报告说，许多消费者似乎面临着消费的“冲动”，他们是否这样做，以及他们如何处理冲动，似乎差异很大。B.收入：体现在资本中的技术变革如何影响工资和人力资本的不平等？可以说，目前和最近生产力的大部分提高都是以这种形式出现的，而关于这一主题的现有工作相当有限。在这里，重点是劳动力市场的摩擦如何影响物质资本和人力资本的积累，以及经济政策如何与这些摩擦相互作用。二.不平等与总量之间的相互作用：a.财富分配对宏观经济有影响吗？本文进一步研究了不平等通过人口储蓄和工作倾向的差异影响总量的渠道。B.政策渠道：经济政策如何影响不平等，反之亦然？这项工作包括：（一）再分配和社会保险的政治经济研究;（二）当决策者因缺乏承诺而受到限制时，对动态政策确定的研究。

The United States economy is one of the richest in the world, both in terms of per capita wealth and in terms of per capita output, but it is also an economy with very sharp contrasts between rich and poor. What is the source of this inequality, and should it concern economists and policy makers? Is it perhaps a natural, or even necessary, aspect of being the richest in the world, or does it reflect a failure that can be addressed with economic policy? And even if inequality per se is not a cause for concern, does it influence aggregate economic activity? Although much progress has been made, academic economists are not yet able to address the above issues in a quantitatively satisfactory way. First, few natural experiments are available to speak directly to the issues using purely empirical methods. Second, adequate economic theory is largely missing. This research addresses the second point: it aims to continue the development of the theory and numerical tools needed for a quantitative study of the sources of inequality and its interrelation with macroeconomics. The present project, in particular, is a continuation of an earlier project (NSF grant #9807760) by this investigator with collaborators. The work proceeds along several fronts, but the common theme is to both develop and apply methods that are of general use in quantitative-theoretical studies of macroeconomics and inequality. The central questions are rather basic ones: What determines how different people save, both in human and physical capital? How does technological change influence wage inequality? How does economic policy influence, and how is it influenced by, inequality? The project has specific applications, but most of the work is on questions of quite broad applicability. The subprojects are as follows: I. Origins of inequality: a. Savings: Why do households differ so much in their propensities to save? This project continues earlier work on the role of initial wealth differences and labor market luck, but also goes further: what determines "discount factors?" The approach here is one of psychology and economics; the psychology literature reports that many consumers seem to face "urges" to consume, and whether they do or not, and how they deal with the urges, seems to vary widely. b. Earnings: How are wage and human capital inequality influenced by technological change that is embodied in capital? Arguably, the bulk of the present and recent improve- ments in productivity take this form, and the existing work on the topic is quite limited. Here, the focus is on how frictions in the labor markets impact both accumulation of physical and human capital, and on how economic policy interacts with these frictions. II. Interactions between inequality and aggregates: a. Does the wealth distribution matter for macro? A further investigation of channels through which inequality-via the differences in propensities to save and work in the population-influences aggregates is undertaken here. b. The policy channel: How does economic policy affect inequality, and vice versa? This work includes (i) a political-economy study of redistribution and social insurance and (ii) a study of dynamic policy determination when policy makers are restricted by a lack of commitment.