New insights on the impact of coefficient instability on ratio-correlation population estimates

In this study we examine the regression-based ratio-correlation method and suggest some new tools for assessing the magnitude and impact of coefficient instability on population estimation errors. We use a robust sample of 904 counties from 11 states and find that: (1) coefficient instability is not a universal source of error in regression models for population estimation and its impact is less than commonly assumed; (2) coefficient instability is not related to bias, but it does decrease precision and increase the allocation error of population estimates; and (3) unstable coefficients have the greatest impact on counties under 20,000 in population size. Our findings suggest that information about the conditions that affect coefficient instability and its impact on estimation error might lead to more targeted and efficient approaches for improving population estimates developed from regression models

EFFECTS OF MANAGEMENT PRACTICES ON GRASSLAND BIRDS: SAVANNAH SPARROW

Information on the habitat requirements and effects of habitat management on grassland birds were summarized from information in more than 4,000 published and unpublished papers. A range map is provided to indicate the relative densities of the species in North America, based on Breeding Bird Survey (BBS) data. Although birds frequently are observed outside the breeding range indicated, the maps are intended to show areas where managers might concentrate their attention. It may be ineffectual to manage habitat at a site for a species that rarely occurs in an area. The species account begins with a brief capsule statement, which provides the fundamental components or keys to management for the species. A section on breeding range outlines the current breeding distribution of the species in North America, including areas that could not be mapped using BBS data. The suitable habitat section describes the breeding habitat and occasionally microhabitat characteristics of the species, especially those habitats that occur in the Great Plains. Details on habitat and microhabitat requirements often provide clues to how a species will respond to a particular management practice. A table near the end of the account complements the section on suitable habitat, and lists the specific habitat characteristics for the species by individual studies. A special section on prey habitat is included for those predatory species that have more specific prey requirements. The area requirements section provides details on territory and home range sizes, minimum area requirements, and the effects of patch size, edges, and other landscape and habitat features on abundance and productivity. It may be futile to manage a small block of suitable habitat for a species that has minimum area requirements that are larger than the area being managed. The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasite of many grassland birds. The section on cowbird brood parasitism summarizes rates of cowbird parasitism, host responses to parasitism, and factors that influence parasitism, such as nest concealment and host density. The impact of management depends, in part, upon a species’ nesting phenology and biology. The section on breeding-season phenology and site fidelity includes details on spring arrival and fall departure for migratory populations in the Great Plains, peak breeding periods, the tendency to renest after nest failure or success, and the propensity to return to a previous breeding site. The duration and timing of breeding varies among regions and years. Species’ response to management summarizes the current knowledge and major findings in the literature on the effects of different management practices on the species. The section on management recommendations complements the previous section and summarizes specific recommendations for habitat management provided in the literature. If management recommendations differ in different portions of the species’ breeding range, recommendations are given separately by region. The literature cited contains references to published and unpublished literature on the management effects and habitat requirements of the species. This section is not meant to be a complete bibliography; a searchable, annotated bibliography of published and unpublished papers dealing with habitat needs of grassland birds and their responses to habitat management is posted at the Web site mentioned below

The division of labor: further exploration in the analysis of an ecological concept

DofL is a core concept in sociology, is usually operationalized in one of two dimensions for the generation of testable hypotheses. The analytic value of the decomposition of DofL into these two dimensions is not without cost for, by focusing on DofL 2, the interrelatedness of the two is ignored, the comparability of data gathered under the same system of occupational classification is restricted by the occasional presence of zero-member categories. This restriction should be evaluated in terms of the C-measure which, by using C.E. Shannon & W. Weaver's conception of information (The Mathematical Theory of Communication, Urbana: U of Illinois Press, 1963), measures the relative cost of information loss incurred when DofL 2 is measured for two sets of data drawn from the same classification scheme, one of which contains zero-member categories. The C-measure is judged to be of potential use for two areas important to the further specification of DofL, ie, replication & cross-cultural research. The C-measure serves as a way to reconcile DofL 1 & DofL 2 so that both dimensions are taken into account in the measurement of DofL

High temperature constitutive and crack initiation modeling of coated single crystal superalloys

The purpose of this program is to develop life prediction models for anisotropic materials used in gas turbine airfoils. In the base portion of the program, two coated single crystal alloys are being tested. They are PWA 286 overlay coated and PWA 273 aluminide coated PWA 1480 and PWA 286 overlay coated Alloy 185. Viscoplastic constitutive models for these materials are also being developed to predict the cyclic stress-strain histories required for life prediction of the lab specimens and actual airfoil designs

Using cohort change ratios to estimate life expectancy in populations with negligible migration: A new approach

Census survival methods are the oldest and most widely applicable methods of estimating adult mortality, and for populations with negligible migration they can provide excellent results. The reason for this ubiquity is threefold: (1) their data requirements are minimal in that only two successive age distributions are needed; (2) the two successive age distributions are usually easily obtained from census counts; and (3) the method is straightforward in that it requires neither a great deal of judgment nor “data-fitting” techniques to implement. This ubiquity is in contrast to other methods, which require more data, as well as judgment and, often, data fitting. In this short note, the new approach we demonstrate is that life expectancy at birth can be computed by using census survival rates in combination with an identity whereby the radix of a life table is equal to 1 (l0 = 1.00). We point out that our suggested method is less involved than the existing approach. We compare estimates using our approach against other estimates, and find it works reasonably well. As well as some nuances and cautions, we discuss the benefits of using this approach to estimate life expectancy, including the ability to develop estimates of average remaining life at any age. We believe that the technique is worthy of consideration for use in estimating life expectancy in populations that experience negligible migration

Brief Note Are Geographic Effects on Life Expectancy in Ohio Spurious Because of Race?

Author Institution: Department of Sociology, Bowling Green State UniversityThe possibility that significant geographic effects on life expectancy found in Ohio may have been spurious because of race is tested in this paper, which utilizes a regression-based technique to estimate life expectancy for selected cities and their suburbs. Using multivariate analysis in conjunction with race-specific regression models we find that, although white life expectancy values exceed those of blacks, the geographic effects described in an earlier paper were not spurious. Because socioeconomic status is associated with both race and geography, these findings provide support for the argument that socioeconomic status plays an instrumental role in differential life expectancy

Geographic Variation of Longevity in Ohio, 1930 and 1980

Author Institution: Department of Sociology, Bowling Green State UniversityAt broad levels (i.e., urban and rural, north and south, state-by-state), variations in longevity have been recorded over time in the United States and elsewhere. However, there is little information on life expectancy variation for specific small areas such as cities and suburbs over time. This is understandable because life expectancy is usually calculated by constructing a life table which has rigorous requirements not usually met by published data for small areas. In this paper, we use a regression-based technique to estimate life expectancy in 1930 and 1980 for selected cities and their suburbs as well as rural counties in Ohio. We examine the variation and changes in life expectancy through multivariate analysis, and find that while differences have narrowed between 1930 and 1980, significant variations in longevity persist among suburban, urban, and rural areas in Ohio