Frailty models with applications to the study of infant deaths on birth timing in Ghana and Kenya

In hazard models, it is assumed that all heterogeneity is captured by a set of theoretically relevant covariates. In many applications however, there are ample reasons for unobserved heterogeneity due to omitted or unmeasured factors. If there is unmeasured frailty, the hazard will not only be a function of the covariates but also of the unmeasured frailty. This paper discusses the implications of unobserved heterogeneity on parameter estimates with application to the analysis of infant death on subsequent birth timing in Ghana and Kenya using DHS data. Using Lognormal Accelerated Failure Time models with and without frailty, we found that standard models that do not control for unobserved heterogeneity produced biased estimates by overstating the degree of positive dependence and underestimating the degree of negative dependence. The implications of the findings are discussed.     

Dynamic redistribution of mitigation resources during influenza pandemics

The Institute of Medicine (IOM) has pointed out that the existing pandemic mitigation models lack the dynamic decision support capability. In this paper, we present a simulation optimization model to generate dynamic strategies for distribution of limited mitigation resources, such as vaccines and antivirals, over a network of regional outbreaks. The model has the capability to redistribute the resources remaining from previous allocations in response to changes in the pandemic progress. The model strives to minimize the impact of ongoing outbreaks and the expected impact of potential outbreaks, considering measures of morbidity, mortality, and social distancing, translated into the societal and economic costs of lost productivity and medical services. The model is implemented on a simulated H5N1 outbreak involving four counties in the state of Florida, U.S. with over four million inhabitants. The performance of our strategy is compared to that of a myopic distribution strategy. Sensitivity analysis is performed to assess the impact of variability of some critical factors on policy performance. The methodology is intended to support public health policy on effective distribution of limited mitigation resources.     

Prospects for food security in the 21st Century: with special emphasis on Africa

Food security for the world in 2025 is possible and probable if the right set of things are done, starting now. But the task will not be easy. It is both a technology and a political/economic challenge. The challenge for sub-Saharan Africa is even greater. While other regions improved per capita food availability over the last 30 years, Africa's availability declined. But food security is about more than supply. It is also about access which means income generating employment is critical. Meeting future requirements in Africa and the world will require sustainable intensification of complex production systems, appropriate national and international policies and continued investments in agricultural research. Without these conditions and increased employment intensive growth, prospects for the future are less bright.     

The Illusory Nature of Balance Sheets in Agricultural Economic Statistics: A Note

Balance sheets are potentially important when monitoring the economic situation of agriculture. As conventionally drawn up, they relate to fictional statistical units and require arbitrary decisions about what constitutes agricultural assets and liabilities. This artificiality undermines their validity. The implications of basing balance sheets on real institutional units are discussed.     

刘小东:时间的证据

今年早些时候,《纽约时报》艺术评论家罗伯塔?史密斯写了篇长文章,指出美国许多美术馆明显偏好后极少主义,是一种视野极端狭窄的表现。这篇极富争议性的文章敦促策展人提高思想独立性,跳出观念艺术一统天下的模式看作品。读完文章,我发现她说得很对,西方不少美术馆在决定哪些作品可以进入当代艺术圣殿上的确存在趣味专制。刘小东的作品就很能说明这个问题。我放下报纸开始想,自己是不是应该站出来向我的纽约同事们为刘小东的绘画、思考以及历史意义正名。于是便有了本文。     

An Intertemporal Currency Board

The paper shows that the traditional wisdom of raising interest rates to defend a currency enriches rather than punishes the speculators. Furthermore, using high interest rates as a currency defense tool often produces the opposite effect in times of crisis. A new approach is proposed of using Hong Kong dollar "put" options as an explicit commitment by the government. The put option itself acts like an intertemporal currency board in keeping the linked exchange rate over time. This costly signaling produces a separating equilibrium that distinguishes the strength of the Hong Kong dollar from the other Asian currencies that were under pressure in 1997.     

Volatility forecasting of exchange rate by quantile regression

Exchange rates are known to have irregular return patterns; not only their return volatilities but the distribution functions themselves vary with time. Quantile regression allows one to predict the volatility of time series without assuming an explicit form for the underlying distribution. This study presents an approach to exchange rate volatility forecasting by quantile regression utilizing a uniformly spaced series of estimated quantiles. Based on empirical evidence of nine exchange rate series, using 19 years of daily data, the adopted approach generally produces more reliable volatility forecasts than other key methods.     

Walgreens重回时代广场“斜线”令世界十字路口耳目一新

巴里温斯顿(Barry Winston),这名专门负责时代广场的标志专家说:“Walgreens已经为入驻时代广场做出了一个新的构想,其中包括一个令人惊叹的LED显示屏,那将是迄今为止在时代广场出现过的最大,最独特的LED显示屏。“     

情定迈阿密——Coppertone女孩和她的小狗标识重新闪耀

这是和Andy Warhol的汤罐一样出名的标志。12月的迈阿密,晴朗的夜晚,Jerry Begins微笑的看着全面翻修的Coppertone女孩带着淘气的咬着她泳衣的可卡犬再次回到城市的MIMO区。Jerry的父亲有家公司Tropicalites,最初是建造和安装标志符号,帮助协调和宣传防晒产品的标志,现在位于比斯坎湾大道北侧7300.