1. Empirical Strategies in Economics: Illuminating the Path From Cause to Effect

经济学中的实证策略:厘清从原因到结果的路径

Joshua D. Angrist

Abstract ：The view that empirical strategies in economics should be transparent and credible now goes almost without saying.

经济学中的经验策略应该是透明和可信的，这种观点现在几乎不用再强调了。

By revealing for whom particular instrumental variables (IV) estimates are valid, the local average treatment effects (LATE) framework helped make this so.

通过揭示特定的工具变量(IV)估计对谁有效，局部平均处理效应的(LATE)框架有助于实现这一点。

This lecture uses empirical examples, mostly involving effects of charter and exam school attendance, to illustrate the value of the LATE framework for causal inference.

本讲座使用实证案例（主要涉及特许学校考试出勤率的影响）来说明因果推断的LATE框架的价值。

LATE distinguishes independence conditions satisfied by random assignment from more controversial exclusion restrictions.

LATE将随机分配应满足的独立条件与更有争议的排除限制区别开来。

A surprising exclusion restriction is shown to explain why enrollment at Chicago exam schools reduces student achievement.

一个令人惊讶的排除限制被证明可以解释为什么芝加哥考试学校的入学考试会降低学生的成绩。

I also make two broader points: IV exclusion restrictions formalize commitment to clear and consistent explanations of reduced-form causal effects; the credibility revolution in applied econometrics owes at least as much to compelling empirical analyses as to methodological insights.

我还提出两个更广泛的观点:工具变量排除限制正式承诺对简化形式因果关系的清晰和一致解释；应用计量经济学的可信性革命至少要归功于令人信服的实证分析，而不是方法论上的洞见。

 

2 Causality in Econometrics: Choice vs Chance

计量经济学中的因果关系：选择与机会

Guido W. Imbens

Abstract ：This essay describes the evolution and recent convergence of two methodological approaches to causal inference.

这篇文章描述了两种因果推断方法的演变和最近的趋同。

The first one, in statistics, started with the analysis and design of randomized experiments.

第一种，在统计学中，从随机实验的分析和设计开始。

The second, in econometrics, focused on settings with economic agents making optimal choices.

第二种，在计量经济学中，关注经济主体做出最佳选择的环境。

 

I argue that the local average treatment effects framework facilitated the recent convergence by making key assumptions transparent and intelligible to scholars in many fields.

我认为，局部平均治疗效果框架通过使许多领域的学者能够透明和理解关键假设，促进了最近的趋同。

Looking ahead, I discuss recent developments in causal inference that combine the same transparency and relevance.

展望未来，我将讨论因果推断的最新发展，这些发展结合了相同的透明度和相关性。

 

3 Robust Empirical Bayes Confidence Intervals

稳健的经验贝叶斯置信区间

Timothy B. Armstrong, Michal Kolesár, Mikkel Plagborg-Møller

Abstract： We construct robust empirical Bayes confidence intervals (EBCIs) in a normal means problem.

我们在正态均值问题中构建了稳健的经验贝叶斯置信区间（EBCI）。

The intervals are centered at the usual linear empirical Bayes estimator, but use a critical value accounting for shrinkage.

置信区间通常以线性经验贝叶斯估计器为中心，但使用考虑收缩的临界值。

Parametric EBCIs that assume a normal distribution for the means (Morris (1983b)) may substantially undercover when this assumption is violated.

假设均值呈正态分布的参数EBCI（Morris （1983b））在违反此假设时可能会大量隐藏。

In contrast, our EBCIs control coverage regardless of the means distribution, while remaining close in length to the parametric EBCIs when the means are indeed Gaussian.

相比之下，无论均值分布如何，我们的EBCI都控制覆盖范围，同时当均值确实是高斯时，其长度与参数EBCI保持接近。

If the means are treated as fixed, our EBCIs have an average coverage guarantee: the coverage probability is at least 1 − α on average across the n EBCIs for each of the means.  

如果均值被视为固定值，则我们的EBCI具有平均覆盖保证：每个均值的n个EBCI的覆盖概率平均至少为1 − α。

Our empirical application considers the effects of U.S. neighborhoods on intergenerational mobility.

我们的实证应用考虑了美国社区对代际流动性的影响。

 

4.General Equilibrium Effects of Cash Transfers: Experimental Evidence From Kenya

现金转移支付的一般均衡效应——来自肯尼亚的实验证据

Dennis Egger, Johannes Haushofer, Edward Miguel, Paul Niehaus, Michael Walker

Abstract ：How large economic stimuli generate individual and aggregate responses is a central question in economics, but has not been studied experimentally.

大规模的经济刺激如何产生个体和总体反应是经济学的核心问题，但尚未进行实验研究。We provided one-time cash transfers of about USD 1000 to over 10,500 poor households across 653 randomized villages in rural Kenya.

我们向肯尼亚农村653个随机村庄的10500多个贫困家庭提供了约1000美元的一次性现金转移支付。

The implied fiscal shock was over 15 percent of local GDP.

隐含的财政冲击超过当地GDP的15%。

We find large impacts on consumption and assets for recipients.

我们发现对接受者的消费和资产有很大的影响。

Importantly, we document large positive spillovers on non-recipient households and firms, and minimal price inflation.

重要的是，我们记录了对非受援家庭和企业的巨大正溢出效应，以及最低的价格通胀。

We estimate a local transfer multiplier of 2.5. We interpret welfare implications through the lens of a simple household optimization framework.

我们估计本地转移乘数为2.5。我们通过简单的家庭优化框架来解释福利影响。

 

5.Uneven Growth: Automation's Impact on Income and Wealth Inequality

增长不平衡：自动化对收入和财富不平等的影响

Benjamin Moll, Lukasz Rachel, Pascual Restrepo

Abstract ：The benefits of new technologies accrue not only to high‐skilled labor but also to owners of capital in the form of higher capital incomes. This increases inequality. To make this argument, we develop a tractable theory that links technology to the distribution of income and wealth—and not just that of wages—and use it to study the distributional effects of automation. We isolate a new theoretical mechanism: automation increases inequality by raising returns to wealth. The flip side of such return movements is that automation can lead to stagnant wages and, therefore, stagnant incomes at the bottom of the distribution. We use a multiasset model extension to confront differing empirical trends in returns to productive and safe assets and show that the relevant return measures have increased over time. Automation can account for part of the observed trends in income and wealth inequality.

摘要：新技术的好处不仅惠及高技能劳动力，也惠及资本所有者，其资本收入较高。这加剧了不平等。为了证明这一论点，我们开发了一种易于处理的理论模型，将技术与收入和财富的分配联系起来，而不仅仅是工资的分配，并用它来研究自动化的分配效应。我们分离出一种新的理论机制：自动化通过提高财富回报来增加不平等。这种回报路径的另一面是，自动化可能导致工资停滞不前，从而导致分配底部的收入停滞不前。我们使用多资产模型扩展来面对生产性和安全资产回报的不同经验趋势，并表明相关的回报措施随着时间的推移而增加。自动化可以解释观察到的收入和财富不平等趋势的一部分。

 

6.Multinationals, Monopsony, and Local Development: Evidence From the United Fruit Company

跨国公司、垄断和地方发展：来自联合水果公司的证据

Esteban Méndez, Diana Van Patten

Abstract This paper studies the role of private sector companies in the development of local amenities. We use evidence from one of the largest multinationals of the 20th century: the United Fruit Company (UFCo). The firm was given a large land concession in Costa Rica—one of the so-called “Banana Republics”—from 1899 to 1984. Using administrative census data with census-block geo-references from 1973 to 2011, we implement a geographic regression discontinuity design that exploits a land assignment that is orthogonal to our outcomes of interest. We find that the firm had a positive and persistent effect on living standards. Company documents explain that a key concern at the time was to attract and maintain a sizable workforce, which induced the firm to invest heavily in local amenities—like the development of education and health infrastructure—that can account for our result. Consistent with this mechanism, we show, empirically and through a proposed model, that the firm's investment efforts increase with worker mobility.

本文研究了私营部门公司在当地基础设施开发中的作用。我们使用20世纪最大的跨国公司之一：联合水果公司（UFCo）的证据。从1899年到1984年，该公司在哥斯达黎加（所谓的“香蕉共和国”之一）获得了大量土地特许权。使用1973年至2011年的人口普查区块地理参考的行政人口普查数据，我们实现了地理回归不连续性设计，该设计利用了与我们感兴趣的结果正交的土地分配。我们发现该公司对生活水平产生了积极而持久的影响。公司文件解释说，当时的一个关键问题是吸引和维持大量的劳动力，这促使公司大力投资当地的便利设施 - 如教育和卫生基础设施的发展 - 这可以解释我们的结果。与这一机制一致，我们通过经验并通过提出的模型表明，公司的投资努力随着工人的流动性而增加。

7.Market Competition and Political Influence: An Integrated Approach

市场竞争与政治影响：一个综合方法

Steven Callander, Dana Foarta, Takuo Sugaya

Abstract The operation of markets and of politics are in practice deeply intertwined. Political decisions set the rules of the game for market competition and, conversely, market competitors participate in and influence political decisions. We develop an integrated model to capture the circularity between the two domains. We show that a positive feedback loop emerges such that market power begets political power, and political power begets market power, but that this feedback loop is bounded. With too much market power, the balance between politics and markets itself becomes lopsided and this drives a wedge between the interests of a policymaker and the dominant firm. Although such a wedge would seem pro-competitive, we show how it can exacerbate the static and dynamic inefficiency of market outcomes. More generally, our model demonstrates that intuitions about market competition can be upended when competition is intermediated by a strategic policymaker.

市场与政治的运行在实践中是紧密交织在一起的。政治决策为市场竞争制定了游戏规则，相反，市场竞争者参与并影响政治决策。我们开发了一个集成模型来捕捉两个领域之间的循环性。结果表明，出现了一个正反馈循环，使得市场力量产生政治权力，政治权力产生市场力量，但这个反馈循环是有界的。由于市场力量过大，政治和市场之间的平衡本身就会变得不平衡，这在政策制定者和占主导地位的公司的利益之间造成了楔子。尽管这样的楔子看起来有利于竞争，但我们展示了它如何加剧市场结果的静态和动态低效率。更一般地说，我们的模型表明，当竞争由战略决策者进行中介时，关于市场竞争的直觉可以被颠覆。

 

8.Productivity Dispersion, Between-Firm Competition, and the Labor Share

生产率分散、企业间竞争与劳动份额

Émilien Gouin-Bonenfant

Abstract I study the effect of labor market imperfections on the labor share in a tractable model that emphasizes the interaction between productivity dispersion and firm competition for workers. I calibrate the model using administrative data covering the universe of firms in Canada from 2000 to 2015. As in the data, most firms have a high labor share, yet the aggregate labor share is low due to the disproportionate effect of a small fraction of large, highly productive firms. I find that a rise in the dispersion of firm productivity causes the aggregate labor share to decline in favor of firm profits. The mechanism is that productivity dispersion effectively shields high-productivity firms from wage competition. Regression evidence from cross-country and cross-industry data supports both the model prediction and mechanism.

通过强调生产率分散与企业竞争之间相互作用的易处理模型，本文研究了劳动力市场不完善对劳动份额的影响。我使用涵盖2000年至2015年加拿大公司范围的行政数据来校准模型。与数据一样，大多数公司的劳动力份额很高，但由于一小部分大型高生产率公司的不成比例的影响，总劳动力份额很低。我发现，企业生产率分散度的上升会导致总劳动份额下降，有利于企业利润。其机制是，生产率分散有效地保护了高生产率企业免受工资竞争的影响。来自跨国和跨行业数据的回归证据支持模型预测和机制。

 

9 The Converse Envelope Theorem

反包络定理

Ludvig Sinander

Abstract I prove an envelope theorem with a converse: the envelope formula is equivalent to a first-order condition. Like Milgrom and Segal's (2002) envelope theorem, my result requires no structure on the choice set. I use the converse envelope theorem to extend to general outcomes and preferences the canonical result in mechanism design that any increasing allocation is implementable, and apply this to selling information.

我从一个反面证明了一个包络定理：包络公式等价于一阶条件。就像Milgrom和Segal（2002）的包络定理一样，我的结果不需要选择集的结构。我使用逆包络定理将机制设计中的规范结果扩展到一般结果和偏好，即任何增加的分配都是可实施的，并将其应用于销售信息。

 

10. A Negishi Approach to Recursive Contracts

递归合约的“根岸”方法

Gaetano Bloise, Paolo Siconolfi

Abstract In this paper, we argue that a large class of recursive contracts can be studied by means of the conventional Negishi method. A planner is responsible for prescribing current actions along with a distribution of future utility values to all agents, so as to maximize their weighted sum of utilities. Under convexity, the method yields the exact efficient frontier. Otherwise, the implementation requires contracts be contingent on publicly observable random signals uncorrelated to fundamentals. We also provide operational first-order conditions for the characterization of efficient contracts. Finally, we compare extensively our approach with the dual method established in the literature.

本文认为，利用传统的根岸方法可以研究一大类递归契约。计划者负责规定当前行动以及向所有代理分配未来效用值，以便最大化其效用加权和。在凸性下，该方法产生精确的有效边界。否则，实现要求合约取决于与基本面无关的可公开观察的随机信号。我们还为有效合同的表征提供操作一阶条件。最后，我们将我们的方法与文献中建立的双重方法进行了广泛的比较。

 

11.Learning From Reviews: The Selection Effect and the Speed of Learning

从评论中学习：选择效果和学习速度

Daron Acemoglu, Ali Makhdoumi, Azarakhsh Malekian, Asuman Ozdaglar

Abstract This paper develops a model of Bayesian learning from online reviews and investigates the conditions for learning the quality of a product and the speed of learning under different rating systems. A rating system provides information about reviews left by previous customers. observe the ratings of a product and decide whether to purchase and review it. We study learning dynamics under two classes of rating systems: full history, where customers see the full history of reviews, and summary statistics, where the platform reports some summary statistics of past reviews. In both cases, learning dynamics are complicated by a selection effect—the types of users who purchase the good, and thus their overall satisfaction and reviews depend on the information available at the time of purchase. We provide conditions for complete learning and characterize and compare its speed under full history and summary statistics. We also show that providing more information does not always lead to faster learning, but strictly finer rating systems do.

摘要 本文建立了在线评论的贝叶斯学习模型，考察了不同评分体系下学习产品质量的条件和学习速度。评级系统提供有关以前客户留下的评论的信息。观察产品的评级，并决定是否购买和评论它。我们在两类评级系统下研究学习动态：完整历史记录，客户可以看到评论的完整历史记录，以及摘要统计信息，平台报告过去评论的一些摘要统计信息。在这两种情况下，学习动态都因选择效应而变得复杂——购买商品的用户类型，因此他们的整体满意度和评论取决于购买时可用的信息。我们为完整的学习提供条件，并在完整的历史记录和汇总统计下表征和比较其速度。我们还表明，提供更多信息并不总是能加快学习速度，但严格来说，更精细的评级系统可以。

 

12. Spatial Correlation Robust Inference

空间相关性稳健推理

Ulrich K. Müller, Mark W. Watson

Abstract We propose a method for constructing confidence intervals that account for many forms of spatial correlation. The interval has the familiar “estimator plus and minus a standard error times a critical value” form, but we propose new methods for constructing the standard error and the critical value. The standard error is constructed using population principal components from a given “worst-case” spatial correlation model. The critical value is chosen to ensure coverage in a benchmark parametric model for the spatial correlations. The method is shown to control coverage in finite sample Gaussian settings in a restricted but nonparametric class of models and in large samples whenever the spatial correlation is weak, that is, with average pairwise correlations that vanish as the sample size gets large. We also provide results on the efficiency of the method.

摘要 提出了一种考虑多种空间相关性的置信区间构造方法。区间具有熟悉的“估计量正减标准误差乘以临界值”形式，但我们提出了构造标准误差和临界值的新方法。标准误差是使用来自给定“最坏情况”空间相关模型的总体主成分构建的。选择临界值以确保空间相关性的基准参数模型中的覆盖范围。该方法被证明可以在有限但非参数类别的模型中控制有限样本高斯设置中的覆盖率，并且在空间相关性较弱时控制大样本中的覆盖率，即平均成对相关性随着样本量变大而消失。我们还提供有关该方法效率的结果。

 

13. Achieving Scale Collectively

集体实现规模化

Vittorio Bassi, Raffaela Muoio, Tommaso Porzio, Ritwika Sen, Esau Tugume

Abstract Many firms in developing countries could be too small to adopt modern technology embodied in expensive production machines. This paper shows that rental market interactions allow these small firms to increase their effective scale and mechanize production. We conduct a survey of manufacturing firms in Uganda, which uncovers an active rental market for large machines between small firms in informal clusters. We then build an equilibrium model of firm behavior and estimate it with our data. We find that the rental market is quantitatively important for mechanization and productivity since it provides a workaround for other market imperfections that keep firms small. The rental market also shapes the effectiveness of development policies to foster mechanization, such as subsidies to purchase machines. Overall, our results point to the importance of taking into account firm-to-firm interactions within informal clusters to understand technology adoption in low income countries: focusing on the small scale of firms in isolation might be misleading.

发展中国家的许多公司可能规模太小，无法采用昂贵的生产机器所体现的现代技术。本文表明，租赁市场的互动使这些小公司能够扩大其有效规模并实现生产机械化。我们对乌干达的制造公司进行了一项调查，发现非正式集群中的小公司之间的大型机器租赁市场活跃。然后，我们建立一个公司行为的均衡模型，并用我们的数据对其进行估计。我们发现，租赁市场在数量上对机械化和生产力很重要，因为它为其他使公司规模较小的市场缺陷提供了一种解决方法。租赁市场也决定了促进机械化的发展政策的有效性，例如对购买机器的补贴。总体而言，我们的研究结果表明，在了解低收入国家的技术采用方面，必须考虑非正式集群内的企业与企业之间的互动：孤立地关注小规模企业可能会产生误导。