Is There a Curse of Dimensionality for Contraction Fixed Points in the Worst Case?

This paper analyzes the complexity of the contraction fixed point problem: compute an ε‐approximation to the fixed point V*Γ(V*) of a contraction mapping Γ that maps a Banach space B_d of continuous functions of d variables into itself. We focus on quasi linear contractions where Γ is a nonlinear functional of a finite number of conditional expectation operators. This class includes contractive Fredholm integral equations that arise in asset pricing applications and the contractive Bellman equation from dynamic programming. In the absence of further restrictions on the domain of Γ, the quasi linear fixed point problem is subject to the curse of dimensionality, i.e., in the worst case the minimal number of function evaluations and arithmetic operations required to compute an ε‐approximation to a fixed point V*∈B_d increases exponentially in d. We show that the curse of dimensionality disappears if the domain of Γ has additional special structure. We identify a particular type of special structure for which the problem is strongly tractable even in the worst case, i.e., the number of function evaluations and arithmetic operations needed to compute an ε‐approximation of V* is bounded by Cε^−p where C and p are constants independent of d. We present examples of economic problems that have this type of special structure including a class of rational expectations asset pricing problems for which the optimal exponent p1 is nearly achieved.     

Anchoring Economic Predictions in Common Knowledge

The paper examines within a unified methodology expectational coordination in a series of economic models. The methodology views the predictions associated with the Rational Expectations Hypothesis as reasonable whenever they can be derived from the more basic Common Knowledge Hypothesis. The paper successively considers a simple non‐noisy N‐dimensional model, standard models with “intrinsic” uncertainty, and reference intertemporal models with infinite horizon. It reviews existing results and suggests new ones. It translates the formal results into looser but economically intuitive statements, whose robustness, in the present state of knowledge, is tentatively ascertained.     

Do Markets Favor Agents able to Make Accurate Predictions?

Blume and Easley (1992) show that if agents' have the same savings rule, those who maximize the expected logarithm of next period's outcomes will eventually hold all wealth (i.e. are ‘most prosperous’). However, if no agent adopts this rule then the most prosperous are not necessarily those who make the most accurate predictions. Thus, agents who make inaccurate predictions need not be driven out of the market. In this paper, it is shown that, among agents who have the same intertemporal discount factor (and who choose savings endogenously), the most prosperous are those who make accurate predictions. Hence, convergence to rational expectations obtains because agents who make inaccurate predictions are driven out of the market.     

“全面二孩”后的人口预期与政策展望

“全面二孩”生育政策究竟能对人口发展产生怎样的影响？文章假定今后维持“全面二孩”人口政策不变进行了人口预测。结果可知：城乡全面放开二孩政策并不会带来出生率的猛增和人口数量的剧烈反弹,高峰期最多可以新增出生人口400万;政策调整会提高人口峰值,有利于改善人口结构,延缓劳动力供给的衰减速度,但作用微乎其微。从其他国家的人口发展经验看,生育率的下降趋势似乎不可避免。因此,“全面二孩”并不是生育政策调整的终点,应继续监测生育水平,进一步调整生育政策;建立和完善“家庭友好”政策体系;从社会体制和经济体制应对负面影响。     

人口生产偏好转变下的农业技术进步

市场化改革以来,中国农村居民的人口生产发生了由高生育率、低人力资本积累率向低生育率、高人力资本积累率的明显转变。这一转变通过农业从业人员数量下降、农村劳动力人力资本水平的提高以及农业物质资本积累的加速,有力地推动了农业技术进步。     

Discrimination,Subjective Wellbeing,and the Role of Gender: A Mediation Model of LGB Minority Stress

ABSTRACT

The present study examined the link between discrimination and the three components of subjective wellbeing (positive and negative affect and life satisfaction) among a cisgender sample of lesbian, gay, and bisexual (LGB) adults. Specifically, we investigated internalized homonegativity and expectations of rejection as potential mediators of the links between discrimination and subjective wellbeing among a sample of 215 participants. Results from our structural equation model demonstrated a strong, positive direct link between discrimination and negative affect. Discrimination also had small, negative indirect effects on life satisfaction through our two mediators. Interestingly, neither discrimination nor our two mediators were related with positive affect, demonstrating the need for future research to uncover potential buffers of this link. Finally, our model evidenced configural, metric, and scalar invariance, suggesting that our model applies well for both women and men. Practical implications and future directions for research are discussed.     

试论时期总和生育率、终身生育率与政策生育率的关系

通过对总和生育率(TFR)、终身生育率(CFR)与政策生育率(PFR)的概念及相关数据分析,论证总和生育率与政策生育率是完全不同的概念,不可直接比较。在特定条件下TFR、CFR和政策生育率会产生差异,在一个国家生育水平下降的历史时期,TFR必然小于当年49岁组女性的CFR;"超生率"、"未婚率"、"未育率"和"不孕率"的变化,决定了政策生育率与终身生育率的差异。借鉴日本经济与人口发展相关数据,可以相信由平均初婚年龄推迟、女性有偶率下降导致的生育水平下降很可能成为对我国人口均衡发展的最大潜在威胁。因此,当前以及今后相当的时期内,我国的政策生育率应高于1.8。     

长白山生育文化的多元性研究

长白山地区在历史上是移民文化、民族文化、外来文化交汇的地区,各种文化互相影响、交汇,形成了当地独具特色的生育文化。在这种生育文化的影响下,长白山地区一直稳定于低生育水平上,少数民族的人口发展也成为全国典范。     

Strategic Supply Function Competition With Private Information

A finite number of sellers (n) compete in schedules to supply an elastic demand. The cost of each seller is random, with common and private value components, and the seller receives a private signal about it. A Bayesian supply function equilibrium is characterized: The equilibrium is privately revealing and the incentives to rely on private signals are preserved. Supply functions are steeper with higher correlation among the cost parameters. For high (positive) correlation, supply functions are downward sloping, price is above the Cournot level, and as we approach the common value case, price tends to the collusive level. As correlation becomes maximally negative, we approach the competitive outcome. With positive correlation, private information coupled with strategic behavior induces additional distortionary market power above full information levels. Efficiency can be restored with appropriate subsidy schemes or with a precise enough public signal about the common value component. As the market grows large with the number of sellers, the equilibrium becomes price‐taking, bid shading is on the order of 1/n, and the order of magnitude of welfare losses is 1/n². The results extend to inelastic demand, demand uncertainty, and demand schedule competition. A range of applications in product and financial markets is presented.     

我国利率政策的有效性研究

在传统IS-LM/AS模型基础上放松三条假设后建立了一个简化的总供需模型,籍此探讨利率政策的价格效应及利率政策的有效性。研究表明,在未完全实现利率市场化的条件下,中国的利率政策存在价格效应,且利率政策在控制货币供应量方面效能较低,易导致短期内价格效应大于需求效应,限制了利率政策的选择空间;总体来看,中国在控制物价过程中倚重于数量型货币政策工具是现阶段的最优选择,可有效化解利率政策的价格效应,促进货币政策有效传导。