编者按：美国全国经济研究所（NBER）是美国最大的经济学研究组织，其发布的工作论文代表着经济学研究最新的成果，每周一发布新论文。本周（9.2-9.8）共发布 22 篇新工作论文，本期将会推送中间 7 篇论文的题目与摘要，供读者学习。
学术财经研究团队翻译。
航空业中的网络竞争：一个实证框架
Zhe Yuan and Panle Jia Barwick #32893
Abstract:The Hub-and-Spoke network is a defining feature of the airline industry. This paper is among the first in the literature to introduce an empirical framework for analyzing network competition among airlines. Airlines make market entry decisions and choose flight frequencies in the first stage, followed by price competition to attract passengers in the second stage. A key feature of this model is the linkage between direct and indirect flights, which is described by a technological relationship (and estimated using data) that proxies the Hub-and-Spoke network. The paper estimates the marginal costs of serving passengers and operating flights using first-order conditions, bounds the entry costs using inequalities derived from the reveal-preference argument, and employs a state-of-the-art econometric method to conduct inference for entry cost parameters. Ignoring network externality underestimates the benefits of operating an additional flight by 13.2%, and airlines would schedule 21.53% fewer one-stop flights had they made flight operation decisions independently for each market. To evaluate the impact of a hypothetical merger, the paper proposes a novel equilibrium concept that makes it feasible to compute the industry equilibria. Counterfactual analyses indicate that a hypothetical merger between Alaska and Virgin America would increase consumer surplus as the merged airline would offer direct flights in 10% more markets while the overall post-merger price effect would likely be muted.
摘要：枢纽辐射网络是航空业的一个关键特征。本文是文献中首批引入实证框架来分析航空公司间网络竞争的研究之一。在模型的第一阶段，航空公司做出市场进入决策并选择航班频率，接着在第二阶段进行价格竞争以吸引乘客。该模型的一个关键特征是直接航班和间接航班之间的联系，这通过一种技术关系（并利用数据进行估计）来描述，作为枢纽辐射网络的代理。本文利用一阶条件估计了服务乘客和运营航班的边际成本，利用由显性偏好论证推导出的不等式来限定进入成本，并采用先进的计量经济学方法对进入成本参数进行推断。忽视网络外部性会低估额外航班运营带来的13.2%的收益，而如果航空公司为每个市场独立做出航班运营决策，它们将减少21.53%的单次中转航班安排。为了评估假设合并的影响，本文提出了一个新的均衡概念，使得计算行业均衡成为可能。反事实分析表明，阿拉斯加航空和维珍美国航空的假设合并将增加消费者剩余，因为合并后的航空公司将在10%的市场中提供直飞航班，而整体合并后的价格效应可能较为温和。
银团贷款的产业构成与银行的气候承诺
Galina Hale, Brigid Meisenbacher, and Fernanda Nechio #32874
Abstract:In the past two decades, a number of banks joined global initiatives aimed to mitigate climate change by “greening” their asset portfolios. We study whether banks that made such commitments have a different emission exposure of their portfolios of syndicated loans than banks that did not. We rely on loan-level information with global coverage combined with country-industry information on emissions. We find that all banks have reduced their loan-emission exposures over the last 8 years. However, we do not find differences between banks that did and those that did not signal their sustainability goals, with the exception of early signers of Principles of Responsible Investments (PRI), who already had lower exposure to emissions through their syndicated lending. In addition, banks that signed PRI shortened the maturity of the loans extended to highly-emitting industries but only temporarily. Thus, we conclude that banks reduced their exposure to climate transition risks on average, but voluntary climate commitments did not contribute to syndicated loan reallocation away from highly-emitting sectors.
摘要：在过去的二十年里，许多银行加入了旨在通过“绿色化”资产组合来减缓气候变化的全球倡议。我们研究了做出此类承诺的银行是否在其银团贷款组合的排放暴露方面与未做出承诺的银行有所不同。我们依赖全球覆盖的贷款级别信息，结合各国各行业的排放数据进行分析。研究发现，所有银行在过去八年中都减少了其贷款的排放暴露。然而，除了早期签署《负责任投资原则》（PRI）的银行以外，我们未发现那些宣示可持续发展目标的银行与未宣示的银行之间存在显著差异。早期签署PRI的银行通过银团贷款已经表现出较低的排放暴露。此外，这些签署了PRI的银行缩短了对高排放行业贷款的期限，但这种变化只是暂时的。因此，我们得出结论，银行整体上减少了对气候转型风险的暴露，但自愿的气候承诺并未促使银团贷款从高排放行业中重新配置。
Too Much of a Good Thing? How Narrow Targeting and Policy Interactions Influence Responses to California’s EITC
好事过多？狭窄的目标定位和政策互动如何影响加利福尼亚州的EITC响应
David Neumark and Zeyu Li #32883
Abstract: California has the highest Earned Income Tax (EITC) supplement to the federal EITC, with an 85% supplement rate. However, we find that despite the apparent generosity of the California EITC, there is no employment effect on less-skilled single mothers, in sharp contrast to the evidence of positive extensive margin effects of other state EITC supplements, and of the federal EITC. Our analysis points to two reasons why, unlike other EITCs, California’s EITC does not appear to have an extensive margin effect. First, most states simply supplement the federal EITC by a fixed percentage. In contrast, in California the maximum credit is reached at a much lower income level, the state EITC begins to phase out as soon as the maximum EITC payment is reached (i.e., there is no plateau), and the phase-out rate is as steep as the phase-in rate. The result is a much higher marginal tax rate that sets in at a much lower income level. Second, California has a very high (and rising) minimum wage. The interaction between a high minimum wage and the unique budget constraint created by the California EITC implies that workers who work more than a relatively low number of hours are unlikely to gain any extra income because of the EITC.
摘要：加利福尼亚州提供的所得税抵免（EITC）补贴比例最高，达到了联邦EITC的85%。然而，我们发现，尽管加州EITC看似慷慨，但对于低技能的单亲母亲来说，并没有产生就业效果，这与其他州的EITC补贴以及联邦EITC的积极广泛效应形成了鲜明对比。我们的分析指出了两个原因，解释了为何加州的EITC与其他EITC不同，没有表现出广泛效应。首先，大多数州只是按固定比例补充联邦EITC。相比之下，加利福尼亚州的最高税收抵免在更低的收入水平就已经达到，州EITC在达到最高EITC付款后立即开始逐步取消（即没有平稳期），且取消率与增幅率一样陡峭。其结果是在更低的收入水平上设定了更高的边际税率。其次，加州的最低工资水平很高（且还在上涨）。高最低工资与加州EITC所创造的独特预算约束之间的相互作用意味着，那些工作时间超过相对较少小时数的工人由于EITC的影响，不太可能获得任何额外收入。
Markups: A Search-Theoretic Perspective
加价：一种基于搜索理论的视角
Guido Menzio #32888
Abstract: I derive a formula for the equilibrium distribution of markups in the search- theoretic model of imperfect competition of Butters (1977), Varian (1980), and Burdett and Judd (1983). The level of markups and the sign of the relationship between a seller’s markup and its size depends on the extent of search frictions, as well as on other deep parameters. Markups are efficient. Markups are positive even though the varieties produced by sellers are perfect substitutes. Markups are heterogeneous even when all sellers operate the same production technology. Markups depend on size, even though the substitutability between a variety and the others does not depend on how much of that variety is consumed. Interpreting these markups through the lens of the monopolistic competition model of Dixit and Stiglitz (1977) would lead one to recover incorrect and unstable buyers’ preferences. Interpreting these markups through the lens of the Dixit-Stiglitz model would also leads to incorrect policy recommendations. These results are a cautionary note on recent work in macroeconomics.
摘要：我推导了在Butters（1977）、Varian（1980）以及Burdett和Judd（1983）的不完全竞争搜索理论模型中的均衡加价分布公式。加价的水平以及卖方加价与其规模之间关系的符号取决于搜索摩擦的程度以及其他深层参数。加价是有效率的。即使卖方生产的品种是完全替代品，加价仍然为正。即使所有卖方使用相同的生产技术，加价也是异质的。即使一种品种与其他品种之间的替代性不依赖于该品种的消费量，加价仍然取决于规模。如果通过Dixit和Stiglitz（1977）提出的垄断竞争模型来解释这些加价，可能会得出错误且不稳定的买方偏好。同样，通过Dixit-Stiglitz模型来解释这些加价也会导致错误的政策建议。上述结果对最近宏观经济学中的研究提出了警示。
Risk, the Limits of Financial Risk Management, and Corporate Resilience
风险、金融风险管理的局限性与企业韧性
René M. Stulz #32882
Abstract:Existing evidence shows convincingly that expected cash flows of non-financial firms can be negatively affected by their total risk, so that non-financial firms can create shareholder wealth by managing their total risk. After reviewing theories that demonstrate links between firm value and total risk, I examine how financial risk management is used to manage firm total risk. I conclude from the evidence that the use of financial risk management is mostly limited to near-term risk in non-financial firms. I offer explanations for this limited role of financial risk management. I argue that the limitations of financial risk management make it important for firms to also focus on resilience and call for more research on the costs and benefits of resilience.
摘要：现有证据明确显示，非金融公司的预期现金流可能会因其总风险而受到负面影响，因此，非金融公司可以通过管理其总风险来创造股东财富。在回顾了展示公司价值与总风险之间联系的理论后，我进一步探讨了金融风险管理在管理公司总风险中的应用。根据证据，我得出结论，金融风险管理在非金融公司中的应用主要限于短期风险。我对此金融风险管理作用有限的原因提供了解释。我认为，金融风险管理的局限性使得公司还需要关注韧性，并呼吁对韧性的成本和收益进行更多研究。
Movements in Yields, not the Equity Premium: Bernanke-Kuttner Redux
收益率的变动，而非股权溢价：伯南克-库特纳重述
Stefan Nagel and Zhengyang Xu #32884
Abstract:We show that the stock market price reaction to monetary policy surprises upon announcements of the Federal Open Market Committee (FOMC) is explained mostly by changes in the default-free term structure of yields, not by changes in the equity premium. We reach this conclusion based on a new model-free method that uses dividend futures prices to obtain the counterfactual stock market index price change that results purely from the change in the default-free yield curve induced by the monetary policy surprise. The yield curve change in turn partly reflects a change in expected future short-term interest rates, as measured by changes in professional forecasts, and partly a change in the term premium. We further find that the even/odd week FOMC cycle in stock index returns is also largely due to an FOMC cycle in the yield curve rather than the equity premium.
摘要：我们发现，在联邦公开市场委员会（FOMC）公告发布时，股票市场对货币政策意外变化的价格反应主要由无违约收益率曲线的变动解释，而不是由股权溢价的变化所驱动。我们基于一种新的无模型方法得出这一结论，该方法利用股息期货价格来获得假设情境下的股票市场指数价格变化，这种变化仅由货币政策意外导致的无违约收益率曲线变化引起。收益率曲线的变化部分反映了未来短期利率预期的变化（由专业预测的变化衡量），部分反映了期限溢价的变化。我们还发现，股票指数回报中的双周FOMC周期主要是由于收益率曲线中的FOMC周期，而不是股权溢价。
学术创业中的性别多样性：社会影响动机与NSF I-Corps项目
April Burrage, Nilanjana Dasgupta, and Ina Ganguli #32885
Abstract: This study examines gender differences in the social impact and commercial motives for academic entrepreneurship using the National Science Foundation's Innovation Corps (NSF I-Corps) program. I-Corps provides experiential entrepreneurship training to faculty and graduate student researchers at local I-Corps university sites and through a nationwide program. Since the inception of I-Corps, only 20% of participants have been women. We first use survey data from one I-Corps university site to show that women participants had higher social entrepreneurial intentions compared to commercial entrepreneurial intentions, and these social entrepreneurial intentions were higher than men’s. We then extend and generalize this finding by analyzing 1,267 publicly available project summaries from the National I-Corps Program from 2012-2019. We find that women PIs’ I-Corps project proposals emphasized social impact significantly more than men PIs, while projects for all PIs emphasized commercial impact to a similar degree. We next ran a field experiment to estimate the causal impact of social impact vs. commercial motives by experimentally manipulating the recruitment email messages inviting researchers to participate in the I-Corps training program. We find that women were more likely to show interest in a social impact version of a message compared to a commercial version, while men showed equal interest in both types of messages. Taken together, our results indicate that women are more interested in pursuing commercialization and entrepreneurship activities when they are tackling societal problems. They suggest that low-cost interventions that emphasize the social impact value of entrepreneurial opportunities may increase gender diversity in entrepreneurship activities.
摘要：本研究通过美国国家科学基金会的创新军团计划（NSF I-Corps）考察了学术创业中社会影响和商业动机的性别差异。I-Corps项目为大学教师和研究生提供创业培训，涵盖本地大学站点和全国性项目。自I-Corps项目启动以来，女性参与者仅占20%。首先，我们利用一个I-Corps大学站点的调查数据表明，女性参与者的社会创业意图高于商业创业意图，并且这些社会创业意图比男性更强烈。然后，我们通过分析2012-2019年间1267个公开可用的全国I-Corps项目总结，扩展和推广了这一发现。我们发现，女性首席研究员的I-Corps项目提案比男性更加强调社会影响，而所有首席研究员的项目对商业影响的重视程度相似。接着，我们进行了一项实地实验，通过实验操控邀请研究人员参与I-Corps培训项目的招募电子邮件信息，以估计社会影响与商业动机的因果影响。结果显示，与商业版本相比，女性对强调社会影响的信息表现出更高的兴趣，而男性对两种类型的信息兴趣相同。综上所述，我们的研究结果表明，女性在解决社会问题时，对商业化和创业活动的兴趣更高。这表明，强调创业机会的社会影响价值的低成本干预措施可能会增加创业活动中的性别多样性。
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