Decision Sciences Volume 30 Number 1 Winter 1999 Printed in the U.S.A. zyxwvutsrq Presenting Geographic Information: Effects of Data Aggregation, Dispersion, and Users’ Spatial Orientation zy Morgan Swink Michigan State Universiv, Department of Marketing and Supply Chain Management, The Eli Broad College zyxwvu of Business, East Lansing, MI 48824, swinkm@pilot.msu.edu Cheri Speier Michigan State Universiv, School of Accounting, The Eli Broad College of Business, East Lansing, MI 48824, cspeier@pilot.msu.edu ABSTRACT Geographic information systems (GIS) have taken on an increasingly important role supporting decision making in many organizations. GIS have been used to support a breadth of tasks including oil and mineral exploration, facility location, logistics sup- port, and facilities management decisions. The effectiveness of GIS as a decision sup- port tool comes primarily from the visual display of data in the form of maps. When presenting information as a geographic map, the level of data aggregation potentially affects aspects of task complexity such as information load and the potential for pattern recognition by the user. Other task attributes expected to be related to data aggregation effects include problem size, the degree of data dispersion, and users’ spatial orientation skills. We conducted an experiment to study these effects and their interactions.Subjects used a GIS including map-based information characterized by different levels of prob- lem size, data dispersion, and data aggregation. Spatial orientation skill was examined as a covariate in the experimental treatments. The results indicate that all of these geo- graphic information characteristics have significant impacts on decision performance. Moreover, many interactions are present among the factors. We evaluate these interac- tions in order to derive implications for practice and for future research. Subject Areas: Decision Support Systems, Geographic Information Systems, and Problem Complexity. INTRODUCTION Businesses are increasingly using geographic information systems (GIS) to sup- port organizational decision making (Payne, 1993; Wagoner zyx & Masser, 1996). GIs is a tool for storing and displaying spatially or geographically related data, provid- ing the decision maker with spatial models and capabilities that can be used to sup- port decision making (Keenan, 1997). As much as 80% of business decisions zy 169