23:T51e,

Limited information about the demand for some of the resources needed to produce goods and services (e.g., incomplete and imperfect bills of materials) forces firms to use heuristics when planning resource capacity. We examine the performance of five heuristics: two drawn from practice, two that modify observed approaches, and one motivated by theory. We measure performance as the ratio of the expected cost of supply–demand mismatch from using a heuristic to the value in the full‐information solution. Numerical analysis shows that a simple heuristic that is common in practice—plan rigorously for a few “driver” resources with high‐quality information and use ratios (e.g., 0.25 indirect labor hours per machine hour) to project the capacities for the remaining “non‐driver” resources—is robust and efficient. Using more than one driver resource to plan for the same non‐driver resource delivers significant gains. Reducing measurement error with respect to the consumption of driver resources dominates the gain from reducing errors in other aspects. Indeed, with high measurement error, collecting information that reduces other sources of error could decrease overall performance. Finally, a greedy algorithm of choosing the most expensive resources as drivers is optimal.

24:T554,

This essay engages with recent work on an unusual, yet fascinating theme: absence. Two edited collections have recently been published that deal with the topic: An Anthropology of Absence: Materializations of Transcendence and Loss (Bille et al., 2010) and The Matter of Death: Space, Place and Materiality (Hockey et al., 2010). These books explore an almost counterintuitive aspect of absence: its material culture. Indeed, absence has a materiality and exists in – and has effects on – the spaces people inhabit and their daily practices and experiences. Drawing on the discussions in these two books and on other recent developments in the study of absence, this essay considers the relational ontology of absence, conceiving absence not as a thing in itself but as something that exists through relations that give absence matter. Absence, in this view, is something performed, textured and materialized through relations and processes, and via objects. We therefore need to trace absence. This entails following and describing the processes through which absence becomes matter and absence comes to matter. It means to map out, locate and follow the traces of absence and understand absences as traces, that is, as residual, incomplete, elusive, ambiguous, yet material entities.

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Capacity planning with limited information

Placing and tracing absence: A material culture of the immaterial