Collaborative Project: Sources of Life-Cycle Inequality

该项目关注生命周期不平等的根源。它的目的可以概括为试图回答两个问题。首先，初始条件和冲击对生命周期不平等有多重要？第二，在初始条件中，哪些对生命周期不平等最重要？为了解决这些问题，该项目通过将风险人力资本框架整合到标准的生命周期永久收入模型中，提供了一个生命周期收益的定量理论。考虑三个初始条件：金融财富、初始人力资本和学习能力。人力资本是有风险的，因为人力资本在每个时期都会受到特殊的冲击。为了使模型具有经验操作性，该项目提供了一种从数据中推断人力资本冲击的方法。选择控制初始条件分布的参数，使模型与一组个体的关键收入事实保持一致：平均收入和收入随年龄分散的上升。当前的宏观经济学工作使用动态模型，其中收入或工资遵循外生的随机过程。该项目超越了目前的工作，提出了一个劳动收入是内生的模型，因为劳动收入是由响应初始条件和随机冲击的最佳人力资本投资决定的。因此，该框架允许将收入和贴现效用的生命周期不平等自然分解为其来源。所提供的框架也适用于对人力资本风险的存在至关重要的政策进行分析。更广泛的影响：在最近的经济研究中，很少有话题比收入、收入和财富不平等及其随时间的变化受到更多的关注。这一研究跨越了经济学的多个领域，包括宏观经济学、劳动力和国际贸易。通过将生命周期不平等分解为其根源，本研究为不平等观察的研究提供了一个补充和关键的视角。理解生命周期不平等的决定因素可以说是至关重要的。它的重要性源于这样一个事实，即更好的、面向数量的理解对于评估政策的相对优点至关重要。所讨论的政策是针对初始条件的政策，例如公共教育，以及提供整个生命周期保险的政策，例如失业保险。这样的理解对于在理论和实证层面上突出未来研究的最重要的边际也是至关重要的。

This project focuses on the sources of life-cycle inequality. Its aim can be summarized as an attempt to answer two questions. First, how important are initial conditions versus shocks for life-cycle inequality? Second, among initial conditions, which are most important for life-cycle inequality? To address these questions, the project offers a quantitative theory of life-cycle earnings by integrating a risky human capital framework into a standard life-cycle, permanent-income model. Three initial conditions are considered: financial wealth, initial human capital, and learning ability. Human capital is risky as human capital is subject to idiosyncratic shocks each period. To make the model empirically operative, the project offers a methodology to infer human capital shocks from data. Parameters governing the distribution of initial conditions are selected so that the model is consistent with key earnings facts for a cohort of individuals: mean earnings and the rise in earnings dispersion with age.Current work in macroeconomics uses dynamic models in which earnings or wages follow exogenous, stochastic processes. This project goes beyond current work by putting forward a model in which labor earnings are endogenous, as labor earnings are determined by optimal human capital investments in response to initial conditions, and stochastic shocks. The framework therefore permits a natural decomposition of life-cycle inequality in earnings and discounted utility into their sources. The framework offered is also appropriate to conduct analyses of policy for which the presence of human capital risk is critical.Broader Impacts: Few topics have received more attention in recent economic research than income, earnings and wealth inequality and their changes over time. This research has spanned several fields in economics, including macroeconomics, labor and international trade. By decomposing life-cycle inequality into its sources, this research provides a complimentary and key perspective for the study of inequality observations. Understanding the determinants of life-cycle inequality is arguably fundamental. Its importance stems from the fact that a better, quantitatively oriented understanding is crucial for the assessment of the relative merits of policies. The policies in question are those directed to initial conditions, e.g., public education, and those that provide insurance over the life cycle, e.g., unemployment insurance. Such an understanding is also vital to highlight the most important margins for future research, both at the theoretical and empirical level.