Elimination of Source A and B Errors in p-Median Location Problems

The p-median problem is a powerful tool in analyzing facility location options when the goal of the location scheme is to minimize the average distance that demand must traverse to reach its nearest facility. It may be used to determine the number of facilities to site, as well as the actual facility locations. Demand data are frequently aggregated in p-median location problems to reduce the computational complexity of the problem. Demand data aggregation, however, results in the loss of locational information. This loss may lead to suboptimal facility location configurations (optimality errors) and inaccurate measures of the resulting travel distances (cost errors). Hillsman and Rhoda (1978) have identified three error components: Source A, B, and C errors, which may result from demand data aggregation. In this article, a method to measure weighted travel distances in p-median problems which eliminates Source A and B errors is proposed. Test problem results indicate that the proposed measurement scheme yields solutions with lower optimality and cost errors than does the traditional distance measurement scheme.     

Disaggregate Migration Behavior and the Volume of Interregional Migration

Nested multinomial logit models are used to investigate migration behavior during the 1971–74 period for a large sample of the population of Ecuador. The nested form of the model makes it possible to test hypotheses about the importance of destination characteristics in conditioning the odds for out-migration. Our empirical results indicate that the odds for migration from each origin are conditioned by the expected utilities of the available set of destinations, as well as characteristics of the origins and the personal characteristics of potential migrants. The association between destination characteristics and the frequency of out-migration allows the total volumes of migration to be adjusted to interregional differences in place-specific utilities.     

Reviews of books

Historical Archaeology -     

Social integration on the Upper Canadian frontier: elements of community in Essex County 1790–1850

Individuals settling new areas have had to rely on a variety of resources, including the social structures inherent in their culture. This study focuses upon the elements of family, kinship and origin in part of nineteenth-century Ontario. It approaches them from the perspectives of interaction over distance and of sociological institution, the particular institution being that of land conveyancing. Data drawn from the surviving parts of the personal and agricultural schedules of the Census of Canada for 1851/52 were searched for the propinquity of individuals to one another. Social interaction seems to have occurred within two miles for most people. Random samples and a series of t-tests suggest that there were no differences in proximity for the members of the different cultural groups but that there were differences between immigrant and established groups with respect to the desires of kin for proximity to one another. These differences were paralleled by differences in the structure of the family. Kinship was also important in determining to whom land was sold; most sales occurred within the particular community. That this was so suggests, according to the model of Steeves, that the level of integration in mid-century Essex was simply embryonic.