Sparse additive models

Summary.  We present a new class of methods for high dimensional non-parametric regression and classification called sparse additive models. Our methods combine ideas from sparse linear modelling and additive non-parametric regression. We derive an algorithm for fitting the models that is practical and effective even when the number of covariates is larger than the sample size. Sparse additive models are essentially a functional version of the grouped lasso of Yuan and Lin. They are also closely related to the COSSO model of Lin and Zhang but decouple smoothing and sparsity, enabling the use of arbitrary non-parametric smoothers. We give an analysis of the theoretical properties of sparse additive models and present empirical results on synthetic and real data, showing that they can be effective in fitting sparse non-parametric models in high dimensional data.     

Intimate partner violence and child abuse: a child‐centred perspective

A substantial body of literature assessing the impact of intimate partner violence on children and associations between intimate partner violence and child abuse now exists. Central to knowledge about these areas of practice and research is a robust, child‐centred consideration of some of the more challenging conceptual issues they give rise to. In this paper, we aim to stimulate debate by presenting a critical, child‐centred perspective on the intersection between intimate partner violence and child abuse. Initially, we provide the context for the review by presenting a brief overview of the literature. We then consider three central issues from a child‐centred perspective. We discuss the language used to describe children forced to live with intimate partner violence, and the importance of hearing children's perspectives on their experiences of such conflict. Finally, we consider similarities and differences between the intimate partner violence and child abuse fields from a child‐centred viewpoint. We conclude that increasing conceptual clarity around these issues will enhance research in the field, and ultimately improve interventions designed to protect children forced to live with intimate partner violence. Copyright © 2009 John Wiley & Sons, Ltd.     

Default and Punishment in General Equilibrium1

We extend the standard model of general equilibrium with incomplete markets to allow for default and punishment by thinking of assets as pools. The equilibrating variables include expected delivery rates, along with the usual prices of assets and commodities. By reinterpreting the variables, our model encompasses a broad range of adverse selection and signalling phenomena in a perfectly competitive, general equilibrium framework. Perfect competition eliminates the need for lenders to compute how the size of their loan or the price they quote might affect default rates. It also makes for a simple equilibrium refinement, which we propose in order to rule out irrational pessimism about deliveries of untraded assets. We show that refined equilibrium always exists in our model, and that default, in conjunction with refinement, opens the door to a theory of endogenous assets. The market chooses the promises, default penalties, and quantity constraints of actively traded assets.     

A flexible model for the pricing of perishable assets

We present a flexible and versatile model which addresses the problem of assigning optimal prices to assets whose value becomes zero after a fixed expiry date. (Such assets include the important example of seats on airline flights.) Our model is broad in scope, in particular encompassing the ability to deal with arrivals of customers in groups. It is highly adaptable and can be adjusted to deal with a very extensive set of circumstances.Our approach to the problem is based on elementary and intuitively appealing ideas. We model the arrival of customers (or groups of customers) according to an inhomogeneous Poisson process. We incorporate into the model time dependent price sensitivity (which may also be described as “time dependent elasticity of demand”). In this setting the solution to the asset pricing problem is achieved by setting up coupled systems of differential equations which are readily amenable to numerical solution via (for instance) a vectorised Runge-Kutta procedure. An attractive feature of our approach is that it unifies the treatment of discrete and continuous prices for the assets.     

The French Nonprofit Sector: A Literature Review

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations -     

A Two-Period Repeated Game Advertising Investment Model for Oligopolistic Markets with an Application to the Beer Industry*

This paper proposes a simple analytical model of advertising competition in oligopoly markets. The widely used log-log sales response function underlies the model specification. Advertising carryover effects are assumed to persist for one period following the period in which the expenditure occurs. Firms are assumed to be engaged in a repeated competitive game in which in every period advertising levels are set such that they maximize current and next period (i.e., two-period) profits. A Nash equilibrium solution is sought for the game. Compared with previous empirical studies of advertising competition in a game theoretic framework, the proposed model offers the following advantages: (1) oligopoly, not duopoly, markets are analyzed; (2) industry sales is allowed to vary over time as a function of advertising expenditures; (3) non-zero discount rates are used for the players. An empirical application is provided using data from the beer market on sales and advertising expenditures of Anheuser-Busch and Miller Brewing. Comparisons are provided with policies that ignore the dependence of next period profits on current advertising levels, reaction function strategies and spending levels obtained from a market share game. Extension of the model formulation to multiple marketing instruments is briefly discussed.     

Planning a crude oil supply system through simulation

This paper will describe the planning of a marine terminal that will supply the water borne crude requirements of an oil refinery. The refinery has experienced a major shift in supply from domestic pipeline crudes to foreign water borne crudes delivered by increasingly large tankers. Sufficient tankage does not exist at the refinery to allow proper segregation, handling and fluctuations in inventory levels caused by the size and uncertainty of tanker arrivals. The major steps involved in this analysis included developing and evaluating alternative proposals for new tankage at the terminal and the refinery. For this purpose, a model was built to simulate the proposed marine terminal and crude deliveries to the refinery. This combined discrete/continuous simulation model was then used to determine the optimal proposal for tankage.     

Does signaling childcare support on job applications reduce the motherhood penalty?

Review of Economics of the Household - There is substantial evidence that due to perceived childcare obligations, mothers are disadvantaged in labor markets. To what extent can childcare support...     

A goal programming model for paper recycling system

The conflict between economic optimization and environmental protection has received wide attention in recent research programs for waste management system planning. This has also resulted in a set of new waste management goals in reverse logistics system planning. The purpose of this analysis is to formulate a mixed integer goal programming (MIGP) model to assist in proper management of the paper recycling logistics system. The model studies the inter-relationship between multiple objectives (with changing priorities) of a recycled paper distribution network. The objectives considered are reduction in reverse logistics cost; product quality improvement through increased segregation at the source; and environmental benefits through increased wastepaper recovery. The proposed model also assists in determining the facility location, route and flow of different varieties of recyclable wastepaper in the multi-item, multi-echelon and multi-facility decision making framework. The use of the model has been illustrated through a problem of paper recycling in India.