A stepwise discrete variable selection procedure

A stepwise variable selection procedure for multinomial discrimination is presented and discussed. Based upon the work of Kullback and Hills, stopping rules are proposed and illustrated for a set of data on communication buyer behavior.     

Bird diversity in a subtropical South-American City: effects of noise levels,arborisation and human population density

Cities are highly modified environments in which the only areas that resemble natural landscapes are urban parks with low human population density. Attempts are frequently made to maintain high bird diversity in cities for aesthetic or educational reasons. However, it remains unclear whether local site characteristics are important in determining bird assemblage composition or whether simplification of the assemblage is an inevitable consequence of the changes associated with human population density. From May 1998 to December 1999, we undertook bird counts at 521 points in Porto Alegre, Rio Grande do Sul, southern Brazil. Our main goal was to understand the pattern of distribution of the bird species richness and density within the city and determine which variables most affect species assemblages. We recorded 132 species belonging to 43 families that are common in Rio Grande do Sul and obtained quantitative data on 121 species in survey sites. The two most abundant species (House Sparrow, Passer domesticus and Rock dove, Columba livia) were exotics. Analysis based on a reduced subset of 134 points surveyed in spring/early summer suggested that there was a North–south gradient in assemblage structure. Variation in assemblage structure was also affected by the number of trees, urban noise and human population density. However, human population density had a much smaller effect on richness and assemblage structure than variables subject to management, such as tree density and noise levels. These results suggest that complex communities may be maintained in densely populated urban areas of sub-tropical South-America given adequate urban planning.     

Getting Out and About: The Relationship Between Urban Form and Senior Travel Patterns

As the overall U.S. population expands outward from the central city and core suburbs and as people age in place, more seniors will reside in suburban and exurban locations. This research seeks to determine whether older adults who live in areas with differing urban forms experience travel pattern variations under controls for other factors related to travel. We analyzed data from a telephone survey of a random sample of seniors aged 75 years and older and we employed a unique approach for establishing the urban form of their residential settings. The results show that urban form does influence travel patterns, including the number of trips and transportation mode, and suggest that the construction of compact, mixed-use communities where today's older adults can age in place may be part of the solution to addressing the mobility needs of our aging population.     

A hypothesis about the decline of fertility

The hypothesis proposed earlier seems to be supported by the analysis of U.S. fertility. Urbanization was consistently negatively correlated with thelevel of fertility in 1810, 1860, 1920, and 1940. Urbanization was not significantly correlated with thedecline of fertility in the period, i.e. from 1800 to 1860; from 1860 to 1920; and from 1920 to 1940. For the period from 1800 to 1860, however, the decline was closely associated with a proxy variable for what is called the spirit of autonomy, i.e., a feeling of control over one's life. It is hypothesized that this sense of control extended to control over fertility. After 1860 the ideas became so widespread that they were no longer associated with any particular group, region, religion, or class. It was just a matter of time until the ideas spread slowly to all groups.     

The Effect of Risk Beliefs on Property Values: A Case Study of a Hazardous Waste Site1

Health risk beliefs of homeowners near a landfill site were assessed in a survey and compared to expert judgments of the health risks of living near the site. A bimodal distribution of health risk beliefs suggested sharp disagreement between the experts and at least some of the residents. Correlates of high risk beliefs included perception of odor from the site, exposure to media coverage of the problem, having children living at home, age (younger respondents more concerned), and gender (females more concerned). An aggregated neighborhood health risk belief predicted reductions in home prices even after controlling for home physical characteristics, such as size and other disamenities such as proximity to a freeway. In the 4100 homes near the site, the estimated depression in property values was estimated to total about $40.2 million before the site was closed and to be about $19.7 million after closure. Implications of these results for community conflict and for benefit-cost analysis of hazard site remediation are discussed.