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Preliminary Steps toward Developing a Sound Research Design for Analyzing the Spatial Distribution of Commercial Hazardous Waste Facilities in Wayne County, Michigan: Part I. March 11, 1998 NRE 501 Robin Saha. General Research Question.
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Preliminary Steps toward Developing a Sound Research Design for Analyzing the Spatial Distribution of Commercial Hazardous Waste Facilities in Wayne County, Michigan: Part I March 11, 1998 NRE 501 Robin Saha
General Research Question Are low income and minority populations disproportionately exposed to the risks associated with commercial hazardous waste facilities in Wayne County, Michigan?
Research Design Issues • Defining geographic areas of impact (“impact zones” or “ host neighborhoods”) • Selecting a geographic unit of analysis (census tracts versus block groups)
Considerations in Defining Impact Zones (Design Issue #1) • Proximity of known or potential impacts • Inverse relationship between distance and impact (social, psychological, economic, environmental, and health ) • Size and shape of geographic units for which demographic data are available • Previous research and comparability with other studies
DESIGN ISSUE #2Considerations in Selecting an Appropriate Unit of Analysis • How different units affect the delineation of host neighborhoods in terms of how well they approximate circular areas • Want to create host neighborhoods (“impact zones”) that are as equivalent as possible in size and shape (equidistant from hazardous waste facilities) -- inter-case consistency
Census Tracts at Least Partially within 1/2 Mile Circle Centered at TSDFs
Census Tracts at Least Partially within 1.0 Mile Circle Centered at TSDFs
1990 Census Tracts Partially within 1.5 Mile Circle Centered at TSDFs
1990 Census Tracts at least Half within 1.5 Mile Circle Centered at TSDFs
Number of Census Tracts Partially within and at Least Half within 1.5 Mile Radius of TSDFs
Area in Decimal Degrees of Census Tracts Partially within and at Least Half within 1.5 Mile Radius of TSDFs
Area of Census Tracts Partially within and at Least Half within 1.5 Mile Radius of TSDFs, as a Percentage of Wayne County
Delineation of Host Neighborhood as Census Tracts Partially Encompassed by Circle of 1.0 Mile Radius #
Delineation of Host Neighborhood as Census Tracts with Area at Least Half within Circle of 1.0 Mile Radius #
Census Tracts Partially within 1.5 Mile Circle Centered at Env’l Waste Control
Census Tract at Least Half within 1.5 Mile Circle Centered at Env’l Waste Control
Block Groups Partially within 1.5 Mile Circle Centered at Env’l Waste Control
Block Groups At Least Half within 1.5 Mile Circle Centered at Env’l Waste Control
Census Tracts Partially within 1.5 Mile Circle Centered at ChemMet
Block Groups Partially within 1.5 Mile Circle Centered at ChemMet
Census Tracts At Least Half within 1.5 Mile Circle Centered at ChemMet
Block Groups At Least Half within 1.5 Mile Circle Centered at ChemMet
Census Tracts within 1.5 Miles of City Environmental Facility X
Block Groups within 1.5 Miles of City Environmental Facility X
“Underlap” and Overlap of Census Tracts within 1.5 Miles of City Environmental X
“Underlap” and Overlap of Block Groups within 1.5 Miles of City Environmental X
Area As a Percentage of 1.5 Mile Circle of Underlap and Overlap for City Environmental
Comparison of Host Neighborhood Delineations Using Census Tracts and Block Groups
Total Population in Host Neighborhoods Using Tracts vs. Combination of Tracts and Block Groups
Selected Demographics of Host Neighborhoods Using Tracts vs. Combination of Tracts and Block Groups
Conclusions Regarding Host Neighborhood Delineations • Areas within a given radius delineate significantly different host neighborhoods using partially vs. mostly circumscribed geographic units (tracts or block groups) • Host neighborhood shape and size can (but do not always) vary significantly depending on whether tracts or block groups are used and urban vs. non-urban locations • Tract/block group differences appear to be insignificant for highly urbanized locations (based on City Env’l TSDF) • Need to repeat analysis for other host neighborhoods, especially for suburban and rural locations
Conclusions Regarding Units of Analysis • Preliminary findings suggest choice of using census tracts or block groups can significantly influence demographic results • These differences need be more carefully assessed before research design decisions regarding most appropriate unit of analysis can be made • Methods for estimating demographic data in “underlap” and overlap areas may address both research design issues
Area in Square Miles of Underlap and Overlap for City Environmental
Census Tracts at Least Partially within 2.0 Mile Circle Centered at TSDFs