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解析文章首发于唧唧堂网站www.jijitang.com
解析作者 | 唧唧堂经济金融写作小组：
文比天大
；审校编辑 |
悠悠
1.时钟拍卖和无线电频谱再分配
摘要：本文研究了在每一轮中降低报价的多轮、多产品时钟采购拍卖的类别。当价格停止下跌时，剩下的竞标者就成了赢家。对于心无旁骛的竞拍者来说，每一个这样的竞拍都有五个不为Vickrey拍卖所共享的属性：每一个都是明显的策略证明和分组策略证明，在相关的第一价格竞拍中设置纳什均衡中标价格，保留中标者关于价值的隐私，并且可以扩展以满足预算约束。在美国激励拍卖的模拟中，该类的启发式时钟拍卖实现了快速计算、高效和低价格。
Abstract：We study the class of multiround, multiproduct clock procurement auctions that reduce offered prices at each round. When prices stop declining, the remaining bidders become the winning sellers. For single-minded bidders, each such auction has five properties not shared by Vickrey auctions: each is obviously strategy-proof and group-strategy-proof, sets prices that are Nash equilibrium winning bids in the related first-price auction, preserves winner privacy about values, and can be extended to satisfy a budget constraint. In simulations of the US incentive auction, a heuristic clock auction from this class achieves quick computations, high efficiency, and low prices.
参考文献：Paul Milgrom and Ilya Sega(2020).Clock Auctions and Radio Spectrum Reallocation.Journal of Political Economy,128(1),1-31.
2.论国家的起源：刚果东部的固定土匪与税收
摘要：对钶钽铁矿石（其大量产出无法隐藏）的积极需求冲击，导致武装分子在钶钽铁矿创建非法海关并提供保护，他们在那里定居为“固定土匪”。对黄金的类似冲击，很容易隐藏，导致在使用黄金收入的村庄出现固定的土匪，他们在那里引入非法采矿签证、税收和管理。民兵或刚果军队的固定土匪可以增加福利。这些发现表明，武装分子可能创造“一个国家的基本职能”，以更好地征用黄金，这取决于他们的目标，可以增加福利。
Abstract：A positive demand shock for coltan, a mineral whose bulky output cannot be concealed, leads armed actors to create illicit customs and provide protection at coltan mines, where they settle as “stationary bandits.” A similar shock for gold, easy to conceal, leads to stationary bandits in the villages where income from gold is spent, where they introduce illicit mining visas, taxes, and administrations. Having a stationary bandit from a militia or the Congolese army increases welfare. These findings suggest that armed actors may create “essential functions of a state” to better expropriate, which, depending on their goals, can increase welfare.
图5 论国家基本职能的强化
参考文献：Raúl Sánchez de la Sierra(2020).On the Origins of the State: Stationary Bandits and Taxation in Eastern Congo.Journal of Political Economy,128(1),32-74.
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3.质量在互联网服务市场中的作用
摘要：在在线采购市场中，项目通常是通过一种机制分配的，这种机制允许买方考虑卖方的非价格特性以及他的出价。本文设计了一种方法，在不可观察的卖方异质性存在的情况下，恢复环境的基本要素，同时适应这类市场的两个重要特征：买方特定的选择集和卖方的高周转率。将研究方法应用于来自在线编程服务市场的数据，以评估与互联网带来的全球化相关的买方福利收益。研究发现，互联网使买方能够大幅改善他们的外部（本地）选择；许多收益来自于进入国际市场。
Abstract：
In online procurement markets, projects are often allocated through a mechanism that allows buyers to take into account a seller’s nonprice characteristics as well as his bid. We design a methodology to recover primitives of the environment in the presence of unobserved seller heterogeneity while accommodating two important features of such markets: buyer-specific choice sets and the high turnover of sellers. We apply our method to data from an online market for programming services, to assess buyers’ welfare gains associated with the globalization enabled by the internet. We find that the internet enables buyers to substantially improve on their outside (local) option; many of the gains arise from access to the international markets.
参考文献：Elena Krasnokutskaya, Kyungchul Song, and Xun Tang(2020).The Role of Quality in Internet Service Markets.Journal of Political Economy,128(1),75-117.
4.过去、现在和未来的劳动力供给：均衡增长的视角
摘要：在战后的美国，工作时间没有规律是一个例外：从各个国家和历史上看，工作时间每年稳步下降略低于0.5%。在宏观经济总量均衡增长的情况下，持续下降的工时是否符合消费和休闲的稳定效用函数？是的。文中充分刻画了这类函数的特征，从而推广了众所周知的“均衡增长偏好”，即需要恒定（而不是下降）的长期工作时间。工时减少的关键是收入效应（生产率稳定增长对工时的影响）略大于替代效应。
Abstract：The absence of a trend in hours worked in the postwar United States is an exception: across countries and historically, hours fall steadily by a little below 0.5% per year. Are steadily falling hours consistent with a stable utility function over consumption and leisure under balanced growth of the macroeconomic aggregates? Yes. We fully characterize the class of such functions and thus generalize the well-known “balanced-growth preferences” that demand constant (as opposed to falling) long-run hours. Key to falling hours is an income effect (of steady productivity growth on hours) that slightly outweighs the substitution effect.
图2 长期的美国工时
图3 1950-2015年选定国家年龄在15至64岁的人均年工时
参考文献：Timo Boppart and Per Krusell(2020).Labor Supply in the Past, Present, and Future: A Balanced-Growth Perspective.Journal of Political Economy,128(1),118-157.
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5.处于有利家庭的儿童0-2岁日托的认知和非认知成本
摘要：利用博洛尼亚日托系统的准入门槛，研究使用断点回归（RD）设计表明，在相对富裕的人群中，在0-2岁时增加一个日托月会使这些小孩到8-14岁时智商降低0.5%（标准差的4.7%）。这种负面影响的程度随着家庭收入的增加而增加。同样的负面影响也存在于人格特征中。这些发现与心理学的假设相一致，即日托儿童与成人的一对一互动较少，这种互动质量较高的家庭会产生负面影响。我们把这个假设嵌入到一个模型中，这个模型为我们的研发设计提供了结构。
Abstract：Exploiting admission thresholds to the Bologna day care system, we show using a regression discontinuity (RD) design that one additional day care month at age 0–2 reduces intelligence quotient by 0.5% (4.7% of a standard deviation) at age 8–14 in a relatively affluent population. The magnitude of this negative effect increases with family income. Similar negative impacts are found for personality traits. These findings are consistent with the hypothesis from psychology that children in day care experience fewer one-to-one interactions with adults, with negative effects in families where such interactions are of higher quality. We embed this hypothesis in a model that lends structure to our RD design.
图A-3 距离密度与最终FAI阈值协变量均值的连续性
参考文献：Margherita Fort, Andrea Ichino, and Giulio Zanella(2020).Cognitive and Noncognitive Costs of Day Care at Age 0–2 for Children in Advantaged Families.Journal of Political Economy,128(1),158-205.
6.递归偏好下异质信仰的生存与长期动态
摘要：本文解析性地描述了一个经济体的长期行为，其中有两种不同的代理人，他们信仰不同，但是却被赋予了相似的递归偏好。当风险规避大于跨期替代弹性的倒数时，具有更不正确信仰的代理人占主导地位，或者从长远来看，信仰不同的代理人共存，因为有很大范围的合理参数化。结果突显了风险分担、投机行为和具有不同信仰的代理人的消费储蓄选择之间的关键交互作用，以及均衡价格在塑造长期结果中的作用。
Abstract：I analytically characterize the long-run behavior of an economy with two types of agents who differ in their beliefs and are endowed with homothetic recursive preferences. Agents with more incorrect beliefs dominate, or agents with different accuracy of their beliefs coexist in the long run, for broad ranges of plausible parameterizations when risk aversion is greater than the inverse of the intertemporal elasticity of substitution. The results highlight a crucial interaction between risk sharing, speculative behavior and consumption-saving choice of agents with heterogeneous beliefs, and the role of equilibrium prices in shaping long-run outcomes.
图2 代理人不同信仰扭曲的生存域
参考文献：Jaroslav Borovička(2020).Survival and Long-Run Dynamics with Heterogeneous Beliefs under Recursive Preferences.Journal of Political Economy,128(1),206-251.
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7.社会保险与婚姻市场
摘要：社会保险往往与婚姻有关。现有的证据表明，婚姻对经济激励的反应很小，这源于在不久的将来实现利益的环境。我分析了将遗属保险与婚姻联系起来对婚姻市场的影响。利用瑞典的取消遗属保险的做法，证明切断这一联系后：（1）影响了在预期赔付前50年的婚姻，（2）使离婚率提高了10%，（3）提高了匹配的多样性。这表明婚姻行为是夫妻计划晚年经济保障策略的关键组成部分。
Abstract：Social insurance is often linked to marriage. Existing evidence suggests small marital responses to financial incentives and stems from settings where benefits are realized in the near future. I analyze how linking survivors insurance to marriage affects the marriage market. Exploiting Sweden’s elimination of survivors insurance, I demonstrate that severing this link (1) affected entry into marriage up to 50 years before expected payout, (2) raised the divorce rate by 10%, and (3) raised the assortativeness of matching. This suggests that marital behavior is a key component of couples’ strategies to plan for financial security in old age.
图3 新婚姻的经验分布
参考文献：Petra Persson(2020).Social Insurance and the Marriage Market.Journal of Political Economy,128(1),252-300.
8.规模经济产业的内外部增长：最优并购政策的计算模型
摘要：文中在一个动态计算模型中研究兼并政策，在该模型中，企业可以通过投资或兼并来降低成本。公司根据这些策略的盈利能力进行投资或提出合并建议。反垄断机构可以以一定的成本阻止合并。我们研究了不能遵守其未来政策的反托拉斯机构的最佳政策，并按照提议的方式批准了合并。我们发现最优政策可能与基于静态福利的政策大不相同。通常，反托拉斯政策会极大地影响公司的投资行为，而公司的投资行为会极大地影响最优的反托拉斯政策。
Abstract：We study merger policy in a dynamic computational model in which firms can reduce costs through investment or through mergers. Firms invest or propose mergers according to the profitability of these strategies. An antitrust authority can block mergers at some cost. We examine the optimal policy for an antitrust authority that cannot commit to its future policy and approves mergers as they are proposed. We find that the optimal policy can differ substantially from a policy based on static welfare. In general, antitrust policy can greatly affect firms’ investment behavior, and firms’ investment behavior can greatly affect the optimal antitrust policy.
图15 箭头显示了最优承诺策略下5个时段的预期过渡
参考文献：Ben Mermelstein, Volker Nocke, Mark A. Satterthwaite, and Michael D. Whinston(2020).Internal versus External Growth in Industries with Scale Economies: A Computational Model of Optimal Merger Policy.Journal of Political Economy,128(1),301-341.
9.比较被选择者：选择竞争时的选择偏差
