Thematic Maps - Notes

The County/Regional Thematic Map Sections continue our visualization of statistical information for the nine counties in the Map Center’s Region. Using Census SF3 data from GeoLytics' CensusCD 2000 and TIGER 2000 line work from ESRI's Arc Data download site we map common themes such as Housing, Education and Income for each county to the Census Tract Level. Regional data is tied to minor civil divisions (municipalities).

Census Tracts are defined by the Census Bureau as "statistical subdivisions of selected counties which are established by a local committee of data users". They are based on several factors such as a threshold population count and established political boundaries within a county. Census Tracts provide a relatively stable basis for tabulating the decennial census data both historically and in an estimating or projecting context. Census Tracts also provide the framework for Census Blocks, the smallest of the Census subdivisions.

On the twelve thematic maps for each county, the county seat and boundaries for Minor Civil Divisions (MCDs): townships, boroughs, towns, cities are included for reference. A link to each county's MCD reference map is provided in the Selector window and at the bottom of each display page. With the exception of the Wyoming and Lackawanna Valleys, Northeastern Pennsylvania is largely rural which means that one Census Tract includes several MCDs. Within the urbanized areas the opposite is true - there are several to many tracts within one MCD.

The regional thematic maps use MCD's directly to create a different view of the thematic data. Although these units are not statistically comparable they do show contrasts between urban and rural areas as well as the county level distribution of the thematic categories. In a few instances the six residents of Centralia, PA were left out of the tabulation in order not to skew the range of values.

The maps employ the choropleth* technique. The data is broken into four ranges using "natural breaks" as a classification scheme. The range values for a particular theme varies among counties. However, graphic and substantive consistency across counties is given highest priority for the Project.

*"Choropleth" is derived from the Greek words CHOROS (place) and PLETH (value). It refers to statistical maps that match distinctive color or shading, representing data, to an enumeration unit which is usually a statistical or administrative area (Census Tracts in this case). See the regional business map page for another example and further information on this technique.