INTRODUCTIONSpatially aggregated data are typically utilized in most location modeling studies. There is, however, a concern that the use of such data may produce unintended effects and perhaps lead to poor decision making. This makes the study of aggregation effects both a relevant and important research area.The necessity for aggregating data arises out of the need to represent and analyze complex spatial systems. Some form of aggregation is associated with most digital representations of spatial information. Location planning studies carried out using spatial optimization models often rely on aggregate data in order to reduce computational effort and facilitate understanding. However, such aggregation must be done without sacrificing the integrity of the spatial structure of the planning area or the needs and objectives of the study. To this end, it is important to assess the quality of optimization model solutions in the context of the original disaggregate data (see Daskin et al. 1989). Analysis on Alan T. Murray andJonathan M. Gottsegen / 201 aggregate data will be useless if it cannot reasonably be interpreted and implemented in the disaggregate form. In other words, analyses using aggregate data must evidence adequate spatial and/or objective function stability when their solutions are mapped back into the original disaggregate structure.
Alan T. Murray is a postdoctoral research fellow at Queensland University of Technology in the AustralianNumerous researchers have investigated some of the inherent issues associated with the use of aggregate data in location planning models. The interest has generally been to identify any biasing influences as well as infer some form of spatial stability in the results of location model solutions. Although some previous research has concluded that the locational results obtained from spatial optimization models using aggregate data are not stable, the issue of stability has been analyzed from a limited perspective. This paper presents a broader analysis of locational results utilizing aggregate data and finds that a significant amount of stability does exist. This is counter to some of the more critical conclusions reached in previous studies, and it suggests that the condemnation of the use of location planning models using aggregate data may be inappropriate.We begin this paper with a review of previous research associated with aggregation analysis. This is followed by a discussion of the analysis approach and the location model utilized in this study. We then present and discuss location model results on data at various degrees of spatial aggregation. We conclude with general comments and suggestions for future research.