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解析文章首发于唧唧堂网站www.jijitang.com
解析作者 | 唧唧堂经济学小组：
文比天大
；审校编辑 |
悠悠 糖糖
1. 社交软件有福利吗？
摘要：社交媒体的兴起既激发了人们对潜在社会利益的乐观预期，也激发了人们对成瘾，抑郁和政治两极分化等危害的担忧。本文通过一项随机实验，发现在2018年美国中期选举之前的四周内停用Facebook，产生了四项活动：（i）减少了在线活动，同时增加了离线活动，例如独自看电视以及与家人和朋友交流；（ii）同时减少事实新闻常识和政治两极化的获取；（iii）增加主观幸福感；（iv）导致实验后Facebook使用量持续大幅减少。停用会降低Facebook的实验后估值，这表明传统指标可能高估了消费者剩余。
Abstract：The rise of social media has provoked both optimism about potential societal benefits and concern about harms such as addiction, depression, and political polarization. In a randomized experiment, we find that deactivating Facebook for the four weeks before the 2018 US midterm election (i) reduced online activity, while increasing offline activities such as watching TV alone and socializing with family and friends; (ii) reduced both factual news knowledge and political polarization; (iii) increased subjective well-being; and (iv) caused a large persistent reduction in post-experiment Facebook use. Deactivation reduced post-experiment valuations of Facebook, suggesting that traditional metrics may overstate consumer surplus.
参考文献：Allcott, Hunt, Luca Braghieri, Sarah Eichmeyer, and Matthew Gentzkow. 2020. "The Welfare Effects of Social Media." American Economic Review, 110 (3): 629-76.
2. 主导货币范式
摘要：本文提出了具有三个主要特征的“主导货币范式”：主导货币定价，价格互补性和生产中的进口投入。使用涵盖91％的世界贸易的2500多个国家/地区的双边价格和数量指数的新构建的数据集，以及哥伦比亚进出口的详细公司产品国家数据，来测试此范式。在这种范式的有力支持下，我们发现：（i）非商品贸易条件与汇率无关；（ii）在价格传递和贸易弹性回归中，美元汇率在数量上主导了双边汇率，这种影响正在增加以美元计价的进口商品所占的份额；（iii）与其他国家的进口相比，美国的进口量对双边汇率的敏感度大大降低；（iv）美元对所有其他货币的升值1％，意味着在控制全球经济周期的情况下，世界其他国家/地区之间的总贸易额将在一年内下降0.6％。并且描述了在这种环境下货币政策冲击的传递和溢出。
Abstract：We propose a "dominant currency paradigm" with three key features: dominant currency pricing, pricing complementarities, and imported inputs in production. We test this paradigm using a new dataset of bilateral price and volume indices for more than 2,500 country pairs that covers 91 percent of world trade, as well as detailed firm-product-country data for Colombian exports and imports. In strong support of the paradigm we find that (i) noncommodities terms-of-trade are uncorrelated with exchange rates; (ii) the dollar exchange rate quantitatively dominates the bilateral exchange rate in price pass-through and trade elasticity regressions, and this effect is increasing in the share of imports invoiced in dollars; (iii) US import volumes are significantly less sensitive to bilateral exchange rates, compared to other countries' imports; (iv) a 1 percent US dollar appreciation against all other currencies predicts a 0.6 percent decline within a year in the volume of total trade between countries in the rest of the world, controlling for the global business cycle. We characterize the transmission of, and spillovers from, monetary policy shocks in this environment.
参考文献：Gopinath, Gita, Emine Boz, Camila Casas, Federico J. Díez, Pierre-Olivier Gourinchas, and Mikkel Plagborg-Møller. 2020. "Dominant Currency Paradigm." American Economic Review, 110 (3): 677-719.
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3. 住房搜索：城市内还是城市间？
摘要：本文研究了由不同客户搜索的具有多个细分市场的房地产市场。在旧金山湾区的城市之间，搜索活动和库存呈负相关，但在城市内的各个细分市场却呈正相关。构建了一个定量搜索模型，该模型显示了广泛搜索者向其搜索范围内的高库存细分市场，研究了其内源性流动如何在具有较大共同客户群的细分市场中的库存与搜索活动之间的关系，呈正相关。搜寻者的普遍存在决定了住房市场对局部供求冲击的反应。广泛的搜索者有助于将冲击分散到许多细分市场，并减少其对本地市场活动的影响。
Abstract：We study housing markets with multiple segments searched by heterogeneous clienteles. In the San Francisco Bay Area, search activity and inventory covary negatively across cities, but positively across market segments within cities. A quantitative search model shows how the endogenous flow of broad searchers to high-inventory segments within their search ranges induces a positive relationship between inventory and search activity across segments with a large common clientele. The prevalence of broad searchers shapes the response of housing markets to localized supply and demand shocks. Broad searchers help spread shocks across many segments and reduce their effect on local market activity.
参考文献：Piazzesi, Monika, Martin Schneider, and Johannes Stroebel. 2020. "Segmented Housing Search." American Economic Review, 110 (3): 720-59.
4. 社会贴现一定要墨守成规吗？
摘要：长期的社会折现率对减缓气候变化，基础设施项目以及其他长期公共政策的价值产生了巨大影响。然而，其价值备受争议，部分原因是由于社交时间偏好的分歧。作者提出了一种“非教条式”社会计划者的理论，他们在当前的规范性判断中缺乏安全感，并承受着可能会改变的可能性。尽管每个非教条式的计划者都提倡跨时期社会福利的特质理论，但所有这些计划者都同意长期的社会贴现率。因此，非教条主义在解决规范分歧方面有一定的作用，特别是对于长期的公共项目。
Abstract：The long-run social discount rate has an enormous effect on the value of climate mitigation, infrastructure projects, and other long-term public policies. Its value is however highly contested, in part because of normative disagreements about social time preferences. I develop a theory of "nondogmatic" social planners, who are insecure in their current normative judgments and entertain the possibility that they may change. Although each nondogmatic planner advocates an idiosyncratic theory of intertemporal social welfare, all such planners agree on the long-run social discount rate. Nondogmatism thus goes some way toward resolving normative disagreements, especially for long-term public projects.
参考文献：Millner, Antony. 2020. "Nondogmatic Social Discounting." American Economic Review, 110 (3): 760-75.
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5. 合作博弈需要监控吗？
摘要：作者由一次重复的游戏出发，该游戏由于监控不完善，无法持续串通。于是添加了一个监视器，该监视器致力于获取公司的私人信息和公共消息。监控器需要定价，以指定获得的信息的精度和作为回报的支付金额。原因如下：首先，由于监控成本低，存在共谋均衡。其次，共谋均衡是监督者所偏爱的。最后，在监督者偏爱的均衡中，企业的收益在折现系数上正在下降。该模型有助于解释利益相关者与美国和欧洲法律行业公司之间的卡特尔协议。
Abstract：I consider a repeated game in which, due to imperfect monitoring, no collusion can be sustained. I add a self-interested monitor who commits to obtain private signals of firms' actions and sends a public message. The monitor makes an offer specifying the precision of the signals obtained and the amount to be paid in return. First, with a low monitoring cost, collusive equilibria exist. Second, collusive equilibria are monitor-preferred. Third, in monitor-preferred equilibria, firms' payoffs are decreasing in the discount factor. My model helps explain cartel agreements between self-interested parties and firms in legal industries in the United States and Europe.
参考文献：Sanktjohanser, Anna. 2020. "Endogenous Monitoring in a Partnership Game." American Economic Review,110 (3): 776-96.
6. 农村建公路，能促进地方经济发展吗？
摘要：全世界有将近十亿人生活在农村地区，这些地区无法获得全国铺设的道路网。作者使用模糊回归不连续性设计以及综合的家庭和公司人口普查微观数据，估算了印度400亿美元的国家农村公路建设计划的影响。道路建设四年后，新的支线道路的主要作用是使工人离开农业。但是，农业成果，收入或资产却没有重大变化。乡村企业的就业略有增长。即使有了更好的市场沟通，偏远地区仍可能继续缺乏经济机会。
Abstract：Nearly one billion people worldwide live in rural areas without access to national paved road networks. We estimate the impacts of India's 40 billion USD national rural road construction program using a fuzzy regression discontinuity design and comprehensive household and firm census microdata. Four years after road construction, the main effect of new feeder roads is to facilitate the movement of workers out of agriculture. However, there are no major changes in agricultural outcomes, income, or assets. Employment in village firms expands only slightly. Even with better market connections, remote areas may continue to lack economic opportunities.
参考文献：Asher, Sam, and Paul Novosad. 2020. "Rural Roads and Local Economic Development." American Economic Review, 110 (3): 797-823.
7. 治疗产妇抑郁症，会对妇女和家庭有影响吗？
摘要：本文评估了治疗产妇抑郁症对女性心理健康，经济能力和养育子女决定的中期影响。文中利用由随机对照试验诱导的变异进行对比，该试验为巴基斯坦农村地区的903名产前抑郁的母亲提供了心理治疗。它是世界上最大的心理治疗干预措施之一，并大大减少了产后抑郁症。心理治疗结束七年后，回到研究地点，发现对女性心理健康的影响持续存在，且抑郁症的患病率降低了17％。这项干预措施还改善了妇女的经济能力，并使时间和金钱密集的父母投资增加了0.2至0.3个标准差。
Abstract：We evaluate the medium-term impacts of treating maternal depression on women's mental health, financial empowerment, and parenting decisions. We leverage variation induced by a cluster-randomized controlled trial that provided psychotherapy to 903 prenatally depressed mothers in rural Pakistan. It was one of the world's largest psychotherapy interventions, and it dramatically reduced postpartum depression. Seven years after psychotherapy concluded, we returned to the study site to find that impacts on women's mental health had persisted, with a 17 percent reduction in depression rates. The intervention also improved women's financial empowerment and increased both time- and money-intensive parental investments by between 0.2 and 0.3 standard deviations.
参考文献：Baranov, Victoria, Sonia Bhalotra, Pietro Biroli, and Joanna Maselko. 2020. "Maternal Depression, Women's Empowerment, and Parental Investment: Evidence from a Randomized Controlled Trial."American Economic Review, 110 (3): 824-59.
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8.财政规则，救助计划和联邦政府声誉
摘要：中央政府对转移支付的期望刺激了地方政府的过度借贷。在本文中，调查询问如果中央政府不能承诺财政规则是否可以减少过度借贷，研究了一个中央政府类型未知的模型，并表明如果中央政府声誉低下，财政规则会增加过度借贷的风险。相反，如果中央政府的声誉很高，则财政规则可以有效地减少债务。即使中央政府的声誉低下，约束性的财政规则也会在信号博弈的均衡中出现。
Abstract：Expectations of transfers by central governments incentivize overborrowing by local governments. In this paper, we ask if fiscal rules can reduce overborrowing if central governments cannot commit to enforce penalties when rules are violated. We study a model in which the central government's type is unknown and show that fiscal rules increase overborrowing if the central government's reputation is low. In contrast, fiscal rules are effective in lowering debt if the central government's reputation is high. Even when the central government's reputation is low, binding fiscal rules will arise in the equilibrium of a signaling game.
参考文献：Dovis, Alessandro, and Rishabh Kirpalani. 2020. "Fiscal Rules, Bailouts, and Reputation in Federal Governments." American Economic Review, 110 (3): 860-88.
9.向不同的投资者融资
摘要：公司从多个投资者那里筹集资金以资助一个项目。仅当所筹集的资金超过随机临界值且该公司由于成功而提供付款时，该项目才能成功。文中研究了企业的最佳实施方案，即保证企业获得最大回报的方案。该计划根据投资者的投资规模向投资者支付不同的净回报（每单位资本）。研究表明，如果投资临界值的分布是对数凹形的，则较大的投资者将获得比较小的投资者更高的净收益。此外，投资者的更大规模会增加公司的收益。分析强调战略风险是不平等的重要潜在驱动因素。
Abstract：A firm raises capital from multiple investors to fund a project. The project succeeds only if the capital raised exceeds a stochastic threshold, and the firm offers payments contingent on success. We study the firm's optimal unique-implementation scheme, namely the scheme that guarantees the firm the maximum payoff. This scheme treats investors differently based on size. We show that if the distribution of the investment threshold is log-concave, larger investors receive higher net returns than smaller investors. Moreover, higher dispersion in investor size increases the firm's payoff. Our analysis highlights strategic risk as an important potential driver of inequality.
参考文献：Halac, Marina, Ilan Kremer, and Eyal Winter. 2020. "Raising Capital from Heterogeneous Investors."American Economic Review, 110 (3): 889-921.
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10.政党选举的博弈
摘要：我们研究两个官职竞逐型政党之间的跨区立法选举，当一个政党具有最初的期望优势时，该优势可能会在竞选期间转移甚至逆转；而且，双方不仅关心赢得多数席位，而且也关心其席位份额。当有利于一个政党的初始失衡很小时，该政党会将中位数选民作为目标。对于适度的失衡，有利的一方保持中心地位，而不利的一方则撤退以其核心支持者为目标；对于巨大的失衡，有利的政党向对手前进，突袭其温和的支持者，以追求绝大多数。
Abstract：We study multi-district legislative elections between two office-seeking parties when one party has an initial valence advantage that may shift and even reverse during the campaign; and, each party cares not only about winning a majority, but also about its share of seats. When the initial imbalance favoring one party is small, each party targets the median voter. For moderate imbalances, the advantaged party maintains the centre-ground, but the disadvantaged party retreats to target its core supporters; and for large imbalances, the advantaged party advances toward its opponent, raiding its moderate supporters in pursuit of an outsized majority.
