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2605.12094 2026-05-13 cs.GT econ.TH

Bayesian Persuasion with a Risk-Conscious Receiver

Yujing Chen

AI总结 本文研究了在接收者使用条件风险价值(CVaR)而非期望效用评估行动的贝叶斯劝说问题。不同于传统的直接推荐方法,CVaR偏好下合并推荐相同行动的信号可能改变接收者的尾部风险排序,破坏激励相容性。作者提出了一种基于后验分布的仿射分片细化方法,建立了主动面揭示原理,并给出了一个精确的多项式规模线性规划模型,从而在有限状态模型中实现了可解性。研究还指出了风险表示的复杂性边界,并提供了一种基于有限精度后验统计量的近似方案。

Comments 32 pages, 3 figures

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英文摘要

We study Bayesian persuasion when the receiver evaluates actions by reward-side Conditional Value-at-Risk (CVaR) rather than expected utility. CVaR preferences break the standard action-based direct-recommendation reduction: merging signals that recommend the same action can change the receiver's tail-risk ranking and destroy incentive compatibility. We show that this failure does not imply intractability in the explicit finite-state model. Each CVaR action value is max-affine in the posterior, and refining recommendations by the active affine piece yields an active-facet revelation principle and an exact polynomial-size linear program. We further identify a representation boundary: listed polyhedral risks remain tractable by the same LP, whereas succinctly represented facet families make exact persuasion NP-hard. Finally, we give a finite-precision approximation scheme for risk preferences determined by finitely many stable posterior statistics.

2605.09642 2026-05-13 econ.GN q-fin.EC

From Expansion to Consolidation: Socio-Spatial Contagion Dynamics in Off-Grid PV Adoption

Roni Blushtein-Livnon, Tal Svoray, Itay Fischhendler, Havatzelet Yahel, Emir Galilee

AI总结 该研究探讨了在无电网地区,社会空间传染效应(SSC)如何影响光伏(PV)技术的扩散过程。研究利用深度学习分割模型,从遥感影像中提取507个无电网聚居区的光伏安装数据,分析了新安装点在已有用户周围的聚集范围与强度,并将其与采用率动态关联。研究发现,SSC在无电网地区普遍存在且强度各异,其影响随时间集中显现,并在扩散初期和后期分别表现出范围扩展和收缩的特征,揭示了从集聚到整合的转变过程,为加速无电网地区光伏推广提供了重要启示。

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英文摘要

In traditional rural societies, where social ties are embedded in physical space, the diffusion of emerging technologies may be amplified through socio-spatial contagion (SSC). Such processes may play a key role in accelerating residential PV adoption in off-grid regions. Yet empirical evidence on SSC in PV adoption remains largely limited to affluent, grid-connected settings, while off-grid regions often lack systematic installation records. To address these gaps, we use a deep learning segmentation model to extract PV installations from a decade-long series of remote sensing imagery across 507 off-grid settlement clusters (hereafter, communities). This enables data-driven spatio-temporal point pattern inference of SSC in data-scarce contexts. SSC is quantified through the range and intensity of clustering of new installations around prior adopters, and the dynamics of these dimensions are linked to adoption outcomes. We found that SSC is nearly ubiquitous, often spanning most of the community's spatial extent, while exhibiting substantial heterogeneity in intensity. Although SSC intensifies over time, its effects remain temporally concentrated, peaking within 1 to 2 years of nearby installations and weakening thereafter. SSC intensity is positively associated with adoption rates in both cross-sectional and temporal analyses. However, the relationship between SSC range and adoption changes over time - in early diffusion phases, adoption growth is associated with range expansion, whereas in later phases it is associated with range contraction. This shift reflects a transition from clustering to consolidation of installations. These findings highlight the potential of seeding interventions to accelerate PV diffusion in off-grid regions.

2512.06946 2026-05-13 econ.EM

Testing the Significance of the Difference-in-Differences Coefficient via Doubly Randomised Inference

Stanisław Marek Sergiusz Halkiewicz, Andrzej Kałuża

AI总结 本文提出了一种基于双重随机化的方法,用于检验双重差分(DiD)估计量的显著性,通过独立地对处理和时间指标进行置换,生成DiD估计量的经验零分布。与传统的OLS $t$-检验、异方差稳健标准误、聚类稳健方差估计等方法相比,该方法在小样本下表现出更好的保守性,并且不受误差分布和方差结构的影响。研究还表明,该双重随机化检验在不同样本规模下均能保持准确的检验水平,且其计算实现已被封装在R包sigDD中,并在实际经济数据中进行了验证。

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This article develops a significance test for the Difference-in-Differences (DiD) estimator based on dual-margin randomization, in which both the treatment and time indicators are independently permuted to generate an empirical null distribution of the DiD estimator. We situate the proposal explicitly within the landscape of existing inference methods for the DiD estimator, including OLS-based $t$-tests, heteroskedasticity-robust standard errors, cluster-robust variance estimators (CRVE), and the recently proposed jackknife standard errors of Hansen (2025). We show that CRVE-based procedures can be severely anti-conservative in small samples, motivating a nonparametric alternative. We formally characterise the permutation space induced by dual randomization, showing that it expands by a factor of $\binom{n}{n_T}$ relative to single-margin permutation tests, and provide an information-theoretic justification for balanced Bernoulli reshuffling. A controlled simulation study, augmented with robustness experiments under non-Gaussian and heteroskedastic errors, demonstrates that the doubly randomised test maintains accurate empirical size at all sample sizes considered, while HC0 and CRVE1 $t$-tests are substantially anti-conservative at small $n$. Crucially, this parametric inflation is driven by the leverage structure of the regressor matrix rather than by the error variance: heteroskedasticity-robust standard errors do not directly address the leverage-driven finite-sample distortion documented here, whereas randomization-based inference is insulated from both error-distributional and variance-structural departures by construction. Power costs relative to the Hansen jackknife test are real but bounded, and become negligible as $n$ grows. The proposed procedure is implemented in the sigDD R package and validated on four empirical datasets from the applied economics literature.

2412.09321 2026-05-13 econ.TH cs.GT

Coarse Q-learning: Indifference, Indeterminacy, and Instability

Philippe Jehiel, Aviman Satpathy

AI总结 本文提出了一种名为粗略Q学习(CQL)的强化学习模型,用于处理具有随机变化选项集的带问题。该模型将选项划分为相似类,并在类内汇总反馈信息以形成类级估值,选择遵循基于类估值的多元逻辑模型,估值则根据实际收益进行更新。研究通过随机逼近方法推导了宏观动态,并揭示了在高收益敏感度下可能出现多种稳定均衡、全局稳定的混合均衡或无稳定均衡等新现象,这些现象源于粗略聚合机制,与标准的选项级模型存在显著差异。

Comments 45 Main pages + 26 Supplemental Appendix pages

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英文摘要

We introduce Coarse Q-learning (CQL), a reinforcement-learning model for bandit problems with stochastically varying menus. Alternatives are exogenously partitioned into similarity classes, and feedback from sampled alternatives is pooled within classes into class-level valuations. Choices follow multinomial logit over class valuations, and valuations update toward realized payoffs as in Q-learning. Using stochastic approximation, we derive the mean-field dynamics and characterize the steady states as smooth analogues of Valuation Equilibria. The model yields novel long-run phenomena in the high payoff-sensitivity limit: depending on the environment, CQL may exhibit multiple stable strict equilibria, a unique globally stable mixed equilibrium with indifference across classes, or no stable equilibrium at all, with valuations and choice probabilities converging instead to a stable limit cycle. These outcomes are driven by coarse aggregation and do not arise in the standard alternative-level benchmark.

2410.07906 2026-05-13 econ.GN q-fin.EC

Structural Change, Employment, and Inequality in Europe: an Economic Complexity Approach

Bernardo Caldarola, Dario Mazzilli, Aurelio Patelli, Angelica Sbardella

AI总结 本文利用2010至2018年欧洲国家的细分产业就业数据,研究产业结构变化对就业增长、工资不平等和收入分配的影响。研究通过构建产业就业矩阵和劳动加权适应度指标,量化了劳动力向复杂产业转移的结构性变化,并发现这种变化虽抑制了就业增长,却降低了收入不平等,同时提升了劳动收入占比,主要源于工资上涨而非新增就业。

Comments 34 pages

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Structural change consists of industrial diversification towards more productive, knowledge intensive activities. However, changes in the productive structure bear inherent links with job creation and income distribution. In this paper, we investigate the consequences of structural change, defined in terms of labour shifts towards more complex industries, on employment growth, wage inequality, and functional distribution of income. The analysis is conducted for European countries using data on disaggregated industrial employment shares over the period 2010-2018. First, we identify patterns of industrial specialisation by validating a country-industry industrial employment matrix using a bipartite weighted configuration model (BiWCM). Secondly, we introduce a country-level measure of labour-weighted Fitness, which can be decomposed in such a way as to isolate a component that identifies the movement of labour towards more complex industries, which we define as structural change. Thirdly, we link structural change to i) employment growth, ii) wage inequality, and iii) labour share of the economy. The results indicate that our structural change measure is associated negatively with employment growth. However, it is also associated with lower income inequality. As countries move to more complex industries, they drop the least complex ones, so the (low-paid) jobs in the least complex sectors disappear. Finally, structural change predicts a higher labour ratio of the economy; however, this is likely to be due to the increase in salaries rather than by job creation.

2409.17035 2026-05-13 econ.GN q-fin.EC

Scaling up to the cloud: Cloud technology use and growth rates in small and large firms

Bernardo Caldarola, Luca Fontanelli

AI总结 该研究探讨了云技术使用对法国企业长期规模增长的影响,发现云服务对企业的增长率有积极影响,尤其是对中小企业而言效果更为显著。研究指出,云技术有助于降低数字化转型的门槛,从而提升企业的可扩展性和增长潜力。这一发现表明,云技术在促进企业增长方面具有重要作用,尤其有利于资源相对有限的中小企业。

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Recent empirical evidence shows that investments in ICT disproportionately improve the performance of larger firms versus smaller ones. However, ICT may not be all alike, as they differ in their impact on firms' organisational structure. We investigate the effect of the use of cloud services on the long run size growth rate of French firms. We find that cloud services positively impact firms' growth rates, with smaller firms experiencing more significant benefits compared to larger firms. Our findings suggest cloud technologies help reduce barriers to digitalisation, which affect especially smaller firms. By lowering these barriers, cloud adoption enhances scalability and unlocks untapped growth potential.

2406.15680 2026-05-13 econ.TH cs.GT

Calibrated Forecasting and Persuasion

Atulya Jain, Vianney Perchet

AI总结 本文研究了一个动态博弈,其中专家向决策者发送概率预测,而决策者通过基于历史数据的校准检验来验证这些预测。专家在通过检验的同时希望最大化自身收益,文章针对平稳遍历过程,将动态博弈转化为静态说服问题,明确了最优预测策略,并揭示了满足校准条件的预测分布特性。研究还比较了有信息和无信息专家的收益差异,并分析了在最小化遗憾的决策者面前,专家所能保证的最低收益水平。

Comments The conference version of this work has been accepted to the Twenty-Fifth ACM Conference on Economics and Computation (EC'24)

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We study a dynamic game where an expert sends probabilistic forecasts to a decision-maker. The decision-maker verifies these forecasts using a calibration test based on past data. How should the expert send forecasts to maximize her payoff while passing the test? For a stationary ergodic process, we characterize the optimal forecasting strategy by reducing the dynamic game to a static persuasion problem. The distributions of forecasts that can arise under calibration are precisely the mean-preserving contractions of the distribution of conditionals. We compare the payoffs attainable by an informed and uninformed expert, providing a benchmark for the value of information. Finally, we consider a regret-minimizing decision-maker and show that the expert can always guarantee at least the calibration benchmark and sometimes strictly more.

2605.11736 2026-05-13 cs.GT econ.TH

Approximate Strategyproofness in Approval-based Budget Division

Haris Aziz, Patrick Lederer, Jeremy Vollen

AI总结 在基于批准的预算分配问题中,研究旨在根据选民对候选人的批准偏好,将可分资源分配给候选人。本文针对Brandl等人提出的不可能性定理,通过引入近似策略证明的概念,探讨了分配规则的激励比,即选民通过操纵所能获得的最大效用增益。研究发现,纳什乘积规则(NASH)具有最优的激励比2,在保持公平性和效率的前提下,有效规避了原有定理的限制,并且该结果在选民具有任意凹效用函数的情况下依然成立。

Comments Forthcoming at IJCAI'26

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In approval-based budget division, the task is to allocate a divisible resource to the candidates based on the voters' approval preferences over the candidates. For this setting, Brandl et al. [2021] have shown that no distribution rule can be strategyproof, efficient, and fair at the same time. In this paper, we aim to circumvent this impossibility theorem by focusing on approximate strategyproofness. To this end, we analyze the incentive ratio of distribution rules, which quantifies the maximum multiplicative utility gain of a voter by manipulating. While it turns out that several classical rules have a large incentive ratio, we prove that the Nash product rule ($\mathsf{NASH}$) has an incentive ratio of $2$, thereby demonstrating that we can bypass the impossibility of Brandl et al. by relaxing strategyproofness. Moreover, we show that an incentive ratio of $2$ is optimal subject to some of the fairness and efficiency properties of $\mathsf{NASH}$, and that the positive result for the Nash product rule even holds when voters may report arbitrary concave utility functions. Finally, we complement our results with an experimental analysis.

2605.11350 2026-05-13 cs.GT cs.AI econ.TH

Human-AI Productivity Paradoxes: Modeling the Interplay of Skill, Effort, and AI Assistance

Ali Aouad, Thodoris Lykouris, Huiying Zhong

AI总结 本文研究了生成式人工智能工具在工作场所和教育中广泛应用背景下,其对生产力影响的复杂机制。作者构建了一个人类与AI互动的模型,分析了技能水平、努力程度与AI辅助之间的相互作用,发现AI的不可靠性或技能发展的内生性可能导致生产力悖论,即更多AI辅助反而降低生产力。此外,研究还揭示了AI对技能分布的长期影响,指出在AI素养存在异质性的情况下,技能极化现象可能在稳态中出现。

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Generative Artificial Intelligence (AI) tools are rapidly adopted in the workplace and in education, yet the empirical evidence on AI's impact remains mixed. We propose a model of human-AI interaction to better understand and analyze several mechanisms by which AI affects productivity. In our setup, human agents with varying skill levels exert utility-maximizing effort to produce certain task outcomes with AI assistance. We find that incorporating either endogeneity in skill development or in AI unreliability can induce a productivity paradox: increased levels of AI assistance may degrade productivity, leading to potentially significant shortfalls. Moreover, we examine the long-term distributional effect of AI on skill, and demonstrate that skill polarization can emerge in steady state when accounting for heterogeneity in AI literacy -- the agent's capability to identify and adapt to inaccurate AI outputs. Our results elucidate several mechanisms that may explain the emergence of human-AI productivity paradoxes and skill polarization, and identify simple measures that characterize when they arise.

2605.11180 2026-05-13 q-fin.GN econ.GN q-fin.EC q-fin.TR

The Value of Information: A Puzzle

Ohad Kadan, Asaf Manela

AI总结 本文研究了信息在金融市场中的价值,指出在温和假设下,知情交易者从信息中获得的总价值可以通过价格变动与订单流之间的协方差来衡量。该协方差反映了噪音交易者的损失,当做市商竞争激烈时,这些损失即为知情交易者的收益。基于美国股票的高频数据估算,平均每只股票每年的信息价值约为350万美元,整体信息价值约为市值的0.04%,远低于投资者每年为寻求超额收益所支付的0.67%费用,文章探讨了这一反直觉结果的可能解释。

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We show that under mild assumptions, the total value of information to informed traders in the market can be measured by the covariance between price changes and order flow. This covariance captures noise trader losses, which equal informed trader gains when market making is competitive. We estimate the value of information using high frequency data on US equities at about $3.5 million per year for the average stock. The aggregate value of information is about 0.04% of market cap, which is considerably lower than the 0.67% in fees investors pay each year searching for superior returns (French 2008). We discuss potential resolutions for these puzzling findings.

2605.11157 2026-05-13 cs.GT cs.AI cs.LG cs.MA econ.TH

The Price of Proportional Representation in Temporal Voting

Nicholas Teh

AI总结 本文研究了在时间投票模型中比例代表制的代价,探讨了比例代表制与社会福利之间的权衡。作者通过最坏情况下的效用比,量化了强制实施比例代表制所带来的效率损失,并发现随着投票轮次或选民数量的增加,这种损失呈亚线性增长。研究还表明,对于较弱的比例代表公理(如正当代表制),随着时间范围的扩大,福利损失会逐渐减小并趋于消失,而更强的公理则始终存在冲突。此外,作者证明了在各类比例代表公理下最大化社会福利是计算复杂的问题,并提出了若干固定参数算法以应对实际场景。

Comments Appears in the 35th International Joint Conference on Artificial Intelligence (IJCAI), 2026

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We study proportional representation in the temporal voting model, where collective decisions are made repeatedly over time over a fixed horizon. Prior work has extensively investigated how proportional representation axioms from multiwinner voting (e.g., justified representation (JR) and its variants) can be adapted, satisfied, and verified in this setting. However, much less is understood about their interaction with social welfare. In this work, we quantify the efficiency cost of enforcing proportionality. We formalize the welfare-proportionality tension via the worst-case ratio between the maximum achievable utilitarian welfare and the maximum welfare attainable subject to a proportionality axiom. We show that imposing proportional representation in the temporal setting can incur a growing, yet sublinear, welfare loss as the number of voters or rounds increases. We further identify a clean separation among axioms: for JR, the welfare loss diminishes as the time horizon grows and vanishes asymptotically, whereas for stronger axioms this conflict persists even with many rounds. Moreover, we prove that welfare maximization under each axiom is NP-complete and APX-hard, even under static preferences and bounded-degree approvals, and provide fixed-parameter algorithms under several natural structural parameters.

2510.14285 2026-05-13 econ.EM math.ST stat.TH

Debiased Kernel Estimation of Spot Volatility in the Presence of Infinite Variation Jumps

B. Cooper Boniece, José E. Figueroa-López, Tianwei Zhou

AI总结 本文研究了在存在无限变差跳跃的情况下,如何对局部波动率进行无偏核估计的问题。作者提出了一种截断核估计方法及其去偏版本,将最优速率的局部波动率估计扩展到更广的跳跃活动指数范围,并建立了相应的中心极限定理。相比以往方法,该方法通过使用更一般的核函数和最优带宽收敛速率,实现了更小的渐近方差,并在更灵活的模型假设下具有更广泛的应用性。仿真研究表明,该方法在有限样本中优于现有方法。

Comments 54 pages

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Volatility estimation is a central problem in financial econometrics, but becomes particularly challenging when jump activity is high, a phenomenon observed empirically in highly traded financial securities. In this paper, we revisit the problem of spot volatility estimation for an Itô semimartingale with jumps of unbounded variation. We construct truncated kernel-based estimators and debiased variants that extend rate-optimal spot volatility estimation to a wider range of jump activity indices, from the previously available bound $Y<4/3$ to $Y<20/11$. Rate-suboptimal CLTs are also established for $Y>20/11$. Compared with earlier work, our approach achieves smaller asymptotic variances through the use of more general kernels and an optimal choice for the bandwidth convergence rate, and also has broader applicability under more flexible model assumptions. A comprehensive simulation study confirms that our procedures outperform competing methods in finite samples.

2508.12471 2026-05-13 econ.GN q-fin.EC

Do High-Premium Fields Buffer Labor Market Shocks? Evidence from India

Jheelum Sarkar

AI总结 本文研究高回报专业领域是否能在劳动力市场危机中为从业者提供更强的保护,以印度为案例,分析新冠疫情对不同技术领域从业者的影响。作者构建了疫情前各技术领域的溢价指标,并采用连续处理的双重差分法,发现高溢价领域对劳动力市场冲击的缓冲作用并非立即显现,而是在疫情后期逐渐体现出来。研究为理解教育回报与劳动力市场韧性之间的关系提供了实证依据。

Comments 13 pages, 4 figures

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Do high-return fields of study provide greater protection in labor market during crises? I construct pre-pandemic premia for major technical fields in India and examine whether workers in higher field-premium fields experience resilient labor market outcomes during COVID-19. Using a difference-in-difference with continuous treatment design, I find that field-premium advantages did not emerge immediately at the onset of the pandemic but through gradual adjustment during later phases.

2506.23619 2026-05-13 q-fin.ST cs.LG econ.EM stat.ML

Overparametrized models with posterior drift

Guillaume Coqueret, Martial Laguerre

AI总结 本文研究了在过度参数化的机器学习模型中,后验漂移对样本外预测准确性的影响。研究发现,当训练与测试样本的数据生成过程参数发生变化时,模型性能会显著下降,这在金融市场等易发生制度变化的场景中尤为重要。应用于股权溢价预测时,研究指出市场择时策略对子时期和模型复杂度参数高度敏感,较小的带宽参数会导致投资回报高度异质,而较大的带宽参数虽能带来更一致的结果,但风险调整后的收益较差,因此在股票市场预测中应谨慎使用大型线性模型。

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This paper investigates the impact of posterior drift on out-of-sample forecasting accuracy in overparametrized machine learning models. We document the loss in performance when the loadings of the data generating process change between the training and testing samples. This matters crucially in settings in which regime changes are likely to occur, for instance, in financial markets. Applied to equity premium forecasting, our results underline the sensitivity of a market timing strategy to sub-periods and to the bandwidth parameters that control the complexity of the model. For the average investor, we find that focusing on holding periods of 15 years can generate very heterogeneous returns, especially for small bandwidths. Large bandwidths yield much more consistent outcomes, but are far less appealing from a risk-adjusted return standpoint. All in all, our findings tend to recommend cautiousness when resorting to large linear models for stock market predictions.

2504.01829 2026-05-13 econ.TH

Revealed Bayesian Persuasion

Jeffrey Mensch

AI总结 本文研究如何通过实证方法检验决策者是否受到贝叶斯劝说的影响。作者提出了一套必要且充分的条件,用于判断观测到的选择数据是否与一个未被观测到的发送者通过最优信号分布进行贝叶斯劝说的行为一致。该研究为信息设计的实证分析提供了一个重要的工具。

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How does one test empirically the hypothesis that a decision maker (DM) is being influenced by information via Bayesian persuasion? In this paper, I consider a DM whose state-dependent preferences are known to an analyst, who sees the conditional distribution of choices given the state. I provide necessary and sufficient conditions for the dataset to be consistent with the DM being Bayesian persuaded by an unobserved sender who generates a distribution of signals to ex-ante optimize the sender's expected payoff. I thereby provide a tool for empirical work on information design.

2407.21198 2026-05-13 econ.TH cs.GT

Lattice operations for the pairwise stable set in many-to-many markets via re-equilibration dynamics

Agustin G. Bonifacio, Noelia Juarez, Paola B. Manasero

AI总结 本文研究了在多对多匹配市场中,当仅对代理人选择函数施加路径独立性条件时,成对稳定集的格运算问题。作者首先证明了企业准稳定匹配和工人准稳定匹配的集合各自构成格结构,然后构建了相应的塔斯基算子,其不动点恰好对应稳定匹配,并证明从合适的准稳定匹配出发迭代这些算子可以得到稳定集中的格运算。这些算子分别类似于裁员动态和职位链动态。

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英文摘要

We compute the lattice operations for the (pairwise) stable set in many-to-many matching markets when only path-independence on agents' choice functions is imposed. To do this, we first show that the sets of firm-quasi-stable and worker-quasi-stable many-to-many matchings form lattices. Then, we construct Tarski operators on these lattices whose fixed points coincide with the set of stable matchings, and show that iterating these operators from suitable quasi-stable matchings yields the lattice operations in the stable set. These operators resemble lay-off and vacancy chain dynamics, respectively.

2007.04267 2026-05-13 econ.EM

Difference-in-Differences Estimators of Intertemporal Treatment Effects

Clément de Chaisemartin, Xavier D'Haultfœuille

AI总结 本文研究了使用面板数据估计跨时期处理效应的方法,处理变量可以是非二元且非吸收性的,结果可能受到处理滞后的影响。作者在平行趋势假设下,提出了一种事件研究估计方法,用于估计在$\ell$个时期内暴露于较弱处理剂量的效应,并提出了归一化估计量以估计当前处理及其滞后效应的加权平均。同时,作者分析了常用的双向固定效应回归方法,指出其在存在异质处理效应时可能存在偏差,而局部投影版本的回归即使在同质效应下也存在偏差。

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英文摘要

We study treatment-effect estimation using panel data. The treatment may be non-binary, non-absorbing, and the outcome may be affected by treatment lags. We make a parallel-trends assumption, and propose event-study estimators of the effect of being exposed to a weakly higher treatment dose for $\ell$ periods. We also propose normalized estimators, that estimate a weighted average of the effects of the current treatment and its lags. We also analyze commonly-used two-way fixed-effects regressions. Unlike our estimators, they can be biased in the presence of heterogeneous treatment effects. A local-projection version of those regressions is biased even with homogeneous effects.