Inventory Models for Substitutable Products: Optimal Policies and Heuristics

In this paper, we examine the nature of optimal inventory policies in a system where a retailer manages substitutable products. We first consider a system with two products 1 and 2 whose total demand is D and individual demands are negatively correlated. A fixed proportion of the unsatisfied customers for an item will purchase the other item if it is available in inventory. For the single-period case, we show that the optimal inventory levels of the two items can be computed easily and follow what we refer to as "partially decoupled" policies, i.e., base stock policies that are not state dependent, in certain critical regions of interest both when D is known and random. Furthermore, we show that such a partially decoupled base-stock policy is optimal even in a multiperiod version of the problem for known D for a wide range of parameter values and in an N-product single-period model under some restrictive conditions. Using a numerical study, we show that heuristics based on the decoupled inventory policy perform well in conditions more general than the ones assumed to obtain the analytical results. The analytical and numerical results suggest that the approach presented here is most valuable in retail settings for product categories where the level of substitution between items in a category is not high, demand variation at the aggregate level is not high, and service levels or newsvendor ratios are high.inventory/production, stochastic multiperiod inventory models, stockout-based substitution

Exploring the Effects of Union-NGO Relationships on Corporate Responsibility: The Case of the Swedish Clean Clothes Campaign

In the current era, governments are playing smaller roles in regulating workers’ rights internationally, and transnational corporations (TNCs), non-governmental organisations (NGOs) involved in the struggle for workers’ rights, and labour/trade unions have started to fill this governance gap. This paper focuses on the least researched of the relationships among these three actors, the union–NGO relationship, by analysing the ways in which it affects definitions of TNC responsibility for workers’ rights at their suppliers’ factories. Based on a qualitative study of the union–NGO relationship in the Swedish garment industry between 1996 and 2005, we propose that there are six main configurations of union–NGO relationships. By linking these configurations to their effects on TNC responsibility, we propose that co-ordination relationships between unions and NGOs, particularly high-commitment co-ordination relationships, are likely to result in a broadening of the definition of TNC responsibility, while conflictual relationships, both high and low commitment, result in a narrowing of the definition of TNC responsibility. The study indicates that co-operation is generally more beneficial for both unions and NGOs than is any form of conflictual relationship, in terms of broadening the definition of TNC responsibility