Deconstructing the Environmental Kuznets Curve: A Theoretical and Empirical Inquiry

本项目开发并测试了预测环境质量水平和时间路径的经济决定因素的理论模型。最近几篇关于经济增长与环境关系的有影响力的论文发现，随着国民收入的增加，许多形式的污染最初会恶化，但随后会改善。针对这些实证发现，许多研究人员提出了所谓的“环境库兹涅茨曲线”（EKC）的理论解释。然而，到目前为止，很少有工作通过在EKC关系的经验估计中加入经济理论的限制来弥合这两种文献之间的差距。如果不理解为什么观察到的污染-收入关系存在，从这些关系中产生的政策含义是模糊的。这项研究将超越收入与污染之间的简化相关性，更密切地研究污染与经济基本面之间的关系。该项目分为五个部分。首先是一项理论调查，以确定污染与人均收入之间的潜在联系。这表明，虽然收入增长本身可以降低污染水平，但收入增长的来源也决定了其污染后果。物质资本积累带来的增长与人力资本获取或技术进步带来的增长会产生不同的污染后果。然后将使用经验方法来表明，包括相关的生产要素，如人力或物质资本，确实改变了污染收入权衡。因此，尚不清楚所观察到的污染-收入关系是由于收入引起的环境政策的加强，还是由于国家产出构成的变化。为了更充分地研究这个问题，项目的其余四个组成部分开发和测试要素积累、收入和污染之间联系的结构模型。第二部分发展和估计了一个简单的污染供求模型。与目前的实证研究相反，它允许经济增长的来源影响其污染后果。与目前的理论工作相比，它允许在功能形式上有足够的灵活性，以纳入目前大多数理论解释的EKC。第三部分考虑了跨界污染和国际贸易的作用。如果污染跨越国界，污染政策应在各国之间联系起来，最优的国内污染政策可能取决于国外的收入水平和要素禀赋。此外，国际相互作用可能大大改变从要素禀赋增长到国内生产污染强度变化的传导机制。最后两节研究跨期决策和政治经济考虑。第三部分承认，环境法规将影响污染密集型生产要素积累的相对回报。从长远来看，提高污染收费会导致因素构成的内生变化，进而影响污染水平。最后，第四部分放宽了所有公民都相同的假设，因此对特定公民的最优污染政策取决于他或她的要素所有权。拥有人力资本的公民数量的增长将产生不同于实物资本增长的后果，这不仅是因为它直接影响到生产中中间产品的使用，而且还因为它将影响到政策偏好的汇总。本建议所述的工作将把经济和环境研究的两个重要领域联系起来：污染-收入关系的简化形式的经验估计，以及环境质量经济决定因素的结构模型。虽然本文所述的工作是初步的，但它确实证明了一种理论影响更大的方法的可行性，以及这种方法在确定有关污染的经济决定因素的政策影响方面的必要性。

This project develops and tests theoretical models predicting the economic determinants of the levels and time paths of environmental quality. Several recent and influential papers on the relationship between economic growth and the environment find that many forms of pollution initially worsen but then improve as national incomes rise. In response to these empirical findings, a number of researchers have proposed theoretical explanations for what has become known as the "Environmental Kuznets Curve" (EKC). As yet, however, there has been little work bridging the gap between these two literatures by adding restrictions from economic theory into the empirical estimation of EKC relationships. Without an understanding of why observed pollution-income relationships exist, policy implications arising from those relationships are ambiguous. This research will go beyond reduced-form correlations between income and pollution to study more closely the relationship between pollution and economic fundamentals. The project is divided into five components. The first is a theoretical investigation to identify potential links between pollution and income per capita. It demonstrates that while increases in income alone can lower pollution levels, the source of the income growth also determines its pollution consequences. Growth arising from physical capital accumulation will have different pollution consequences than growth arising from human capital acquisition or technological progress. Empirical methods will then be used to show that the inclusion of relevant factors of production, such as human or physical capital, does indeed alter pollutionincome trade-offs. As a result, it is unclear whether the observed pollution-income relationship arises from income-induced strengthening of environmental policy or from changes in the composition of nations' output. To investigate this question more fully, the remaining four components of the project develop and test structural models of the links between factor accumulation, income, and pollution. The second component develops and estimates a simple model of pollution demand and supply. In contrast to current empirical work it allows the sources of economic growth to affect its pollution consequences. In contrast to current theoretical work it allows for sufficient flexibility in functional forms as to incorporate most of the current theoretical explanations for the EKC. The third component considers the role of transboundary pollution and international trade. If pollution crosses borders, pollution policies should be linked across countries, and the optimal domestic pollution policy may depend on income levels and factor endowments abroad. Furthermore, international interactions may considerably alter the transmission mechanism from growth in factor endowments to changes in the pollution-intensity of domestic production. The final two sections study intertemporal decision making and political economy considerations. The third section recognizes that environmental regulations will affect the relative return to accumulating pollution-intensive factors of production. Rising pollution charges lead to endogenous changes in the long run composition of factors that in turn affects pollution levels. Finally, the fourth section relaxes the assumption that all citizens are identical, so that the optimal pollution policy for a given citizen depends on his or her factor ownership. Growth in the number of human-capital holding citizens will have different consequences than growth in physical capital, not only because of the direct implications on the use of intermediates in production, but also because it will affect the aggregation of preferences into policy. The work described in this proposal will link two important areas of economic and environmental research: reduced-form empirical estimates of the pollution-income relationship, and structural models of the economic determinants of environmental quality. While the work described herein is preliminary, it does demonstrate the feasibility of a more theoretically influenced approach and the necessity of such an approach for drawing policy implications about the economic determinants of pollution.