Mapping Market Areas Using Nonparametric Smoothing

A new method is proposed to map firms' principal market areas using shipment data. The new method is a general one which could prove just as useful in mapping the incidence of disease as in mapping market areas. This method is applied to agricultural data for feeder cattle sales at a video cattle auction. Transportation costs appear to be the main determinant of market area boundaries, but there are many cases where transportation costs alone cannot explain the market areas found. The size and shape of market areas for feeder cattle buyers are large, irregularly shaped, and extensively overlapping.     

Parameterization and Visualization of the Errors in Areal Interpolation

Areal interpolation involves the transfer of data from one zonation of a region to another, where the two zonations of space are geographically incompatible. By its very nature this process is fraught with errors. However, only recently have there been specific attempts to quantify these errors. Fisher and Langford (1995) employed Monte Carlo simulation methods, based on modifiable areal units, to compare the errors resulting from selected areal interpolation techniques. This paper builds on their work by parameterizing and visualizing the errors resulting from the areal weighting and dasymetric methods of areal interpolation. It provides the basis for further research by developing the methodology to produce predictive models of the errors in areal interpolation. Random aggregation techniques are employed to generate multiple sets of source zones and interpolation takes place from these units onto a fixed set of randomly generated target zones. Analysis takes place at the polygon, or target zone level, which enables detailed analysis of the error distributions, basic visualization of the spatial nature of the errors and predictive modeling of the errors based on parameters of the target zones. Correlation and regression analysis revealed that errors from the areal weighting technique were related to the geometric parameters of the target zones. The dasymetric errors, however, demonstrated more association with the population or attribute characteristics of the zones. The perimeter, total population, and population density of the target zones were shown to be the strongest predictive parameters.     

Two-Way Migration in a Model with Identical Optimizing Agents

The simplest migration models based on maximizing behavior assume movement toward more desirable locations, and therefore ignore the large portion of moves in the "wrong" direction. Based on a model with identical, utility-maximizing agents, the analysis below shows that changes in relative location attractiveness can cause many migrants to move against the dominant stream. Even when the population distribution is stable and variation in wages and prices across locations reflect compensating differentials, so locations are equally attractive, individuals choose to move between locations, spending parts of their lives in different locations. These results stem from the role of consumption opportunities in migration decisions, highlighting processes that have been largely ignored.     

Laplace schreibt nach Gotha

Around 1800, Laplace had an intense correspondence with his colleagues in Gotha on problems in celestial mechanics, especially on the lunar theory. Most of these letters are not included in Roger Hahn's New calendar of the correspondence of P. S. Laplace (1994).     

Georges Ungar and memory transfer

The idea that memories could be transferred from one organism to another by administration of a "trained" donor brain to a naive recipient seized both scientific and public attention in the 1960's and early 1970's. Georges Ungar was one of the earliest and strongest proponents of this idea, and he provided it extensive theoretical and experimental support. This paper reviews Ungar's work on memory transfer (and in particular on the scotophobin molecule), with an analysis of its successes and failures.