Robust supply base management: Determining the optimal number of suppliers utilized by contractors

The importance of robust supply base management under demand uncertainty requires an understanding of the benefits associated with a contractor having an optimal number of suppliers. The key benefit is a reduction in a contractor's total cost of supply base management. However, few supplier-optimizing models incorporate the perspectives of both demand uncertainty and supply base management costs. The objective of this paper is twofold: (1) to investigate the dynamics between demand uncertainty and coordination; and (2) to develop a model that determines the optimal number of suppliers that a contractor should maintain in its supply base to become more flexible and maximize its profits.     

The market price of risk and the equity premium: A legacy of the Great Depression?

By positing learning and a pessimistic initial prior, we build a model that disconnects a representative consumer's subjective attitudes toward risk from the high price of risk that a rational-expectations econometrician would deduce from financial market data. We follow Friedman and Schwartz [1963. A Monetary History of the United States, 1857-1960. Princeton University Press, Princeton, NJ] in hypothesizing that the Great Depression heightened fears of economic instability. We use a robustness calculation to elicit a pessimistic prior for a representative consumer and let him update beliefs via Bayes’ law. Learning eventually erases pessimism, but while it persists, pessimism contributes a volatile multiplicative component to the stochastic discount factor that a rational-expectation econometrician would detect. With sufficient initial pessimism, the model generates substantial values for the market price of risk and equity premium and predicts high Sharpe ratios and forecastable excess stock returns.     

需求不确定下闭环供应链生产计划优化研究

针对需求环境不确定的再制造闭环供应链,采用基于情景分析的鲁棒优化方法,建立基于物料需求计划的产品再制造闭环供应链生产计划运作鲁棒优化模型.制造商和供应商在整个供应链系统协调稳定运行的前提下,追求各自的期望利润最大化.并介绍了需求环境的变动给整个闭环供应链系统带来的影响,为企业生产计划的制订提供了解决方案.案例数值的结果也直接验证了该模型的Robust性.     

Robust implementation in general mechanisms

A social choice function is robustly implemented if every equilibrium on every type space achieves outcomes consistent with it. We identify a robust monotonicity condition that is necessary and (with mild extra assumptions) sufficient for robust implementation.Robust monotonicity is strictly stronger than both Maskin monotonicity (necessary and almost sufficient for complete information implementation) and ex post monotonicity (necessary and almost sufficient for ex post implementation). It is equivalent to Bayesian monotonicity on all type spaces.     

‘GUNS OR BUTTER?’ REVISITED: ROBUSTNESS AND NONLINEARITY ISSUES IN THE DEFENSE–GROWTH NEXUS

The relationship between military expenditure and growth is studied taking into account potential nonlinearities and robustness issues in the specification of the econometric models used. Using cross‐country growth regressions and the widely used Feder–Ram model, the partial correlation between defense spending and economic growth appears robust and significantly negative only for countries with a relatively low military expenditure ratio. While the externality effect appears positive in this subgroup of countries, the overall effect turns negative due to the size effect of the military sector.     

Robust supply chain management

Faced with uncertainty, researchers have explored concepts such as robustness, flexibility, information structure, options, and market power for supply chain management. Despite many influential findings, such as the presence of the bullwhip effect and channel power, the literature in supply chain management is a bit confusing with regard to these concepts, including how they are related to each other. In light of this, we discuss the meaning of the terms in a supply chain management context. We indicate what questions are at stake and some pitfalls to be aware of if the phenomenon we are concerned about is affected by strategic players. This paper is modelling focused.     

A robustness study of a multi-echelon inventory model via simulation

This paper examines the robustness of a standard model of multi-echelon inventory systems, specifically the models discussed in Axsäter (Oper. Res. 48(5) (2000) 686). A simulation model was developed to explore the model's ability to predict system performance for a two-echelon one-warehouse, multiple retailer system using (R,Q) inventory policies under conditions that violate the model's fundamental modeling assumptions. In particular, the impact of non-stationary demand on this stationary demand inventory model was examined. The model performs well at the low demand and large retailer order batch size situations, but our testing of the model indicated that care must be taken when applying this model to situations that violate its fundamental assumption. These results should help practitioners to better understand the assumptions of these models and to determine when or when not to apply these models in practice.     

On the robustness of persistence in mutual fund performance

This paper analyzes persistence in US equity mutual fund performance over the period 1990–2015. We apply commonly used measures of persistence, which we test using a set of simulated passive funds. In the first stage we apply contingency tables and transition matrices in accordance with previous literature. Results show how these methodologies are biased towards finding evidence of persistence too easily. In the second stage, we take a recursive portfolio approach, which assesses the performance of investing by following recommendations based on past performance. Results show the importance of both estimating persistence by distinguishing among fund style groups, and considering the cross-sectional significance of recursive portfolios. In general, our results support evidence of persistence in mutual fund performance, especially for the case of the best mutual funds. However, this evidence does not hold for the most recent subperiod, 2008–2015. Empirical evidence of persistence is conditioned by the sample period, a result that could explain the inconclusive results found in the literature.     

Model uncertainty and intertemporal tax smoothing

In this paper we examine how model uncertainty due to the preference for robustness (RB) affects optimal taxation and the evolution of debt in the Barro tax-smoothing model (1979). We first study how the government spending shocks are absorbed in the short run by varying taxes or through debt under RB. Furthermore, we show that introducing RB improves the model׳s predictions by generating (i) the observed relative volatility of the changes in tax rates to government spending, (ii) the observed comovement between government deficits and spending, and (iii) more consistent behavior of government budget deficits in the U.S. economy. Finally, we show that RB can also improve the model׳s predictions in the presence of multiple shocks.     

Stability of the World Trade Web over time – An extinction analysis

The World Trade Web (WTW) is a weighted network whose nodes correspond to countries while edge weights reflecting the value of imports and/or exports between countries. In this paper we introduce to this macroeconomic system the notion of extinction analysis, a technique often used in the analysis of ecosystems, for the purpose of investigating the robustness of this network. In particular, we subject the WTW to a principled set of in silico “knockout experiments,” akin to those carried out in the investigation of food webs, but suitably adapted to this macroeconomic network. Informed by results in network theory as well as studies of contagion in economic networks, we seek to understand the role of connectance in the robustness of the system. We interpret increasing connectance as one aspect of a move towards globalization and liberalized trade policy. Broadly, our experiments confirm two conjectures. First, that the WTWs are “robust yet fragile” networks — robust to random failures but fragile under targeted attack. Second, that growing connectance has both positive and negative impacts on robustness. More specifically, we find that increasing connectance corresponds to increasing robustness for small shocks but to decreasing robustness in the face of large, cascading shocks up to the system. This yields evidence in support of the view that globalization, as witnessed by increasing connectance, increases the ability of a system to absorb shock up until a certain size, whereupon the shock overwhelms the system and sparks a broader contagion. We anticipate that experiments and measures like these can play an important role in the evaluation of the stability of economic systems.