Measuring A Gerrymander |
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Gerrymander - refers to the drawing of boundaries of legislative districts to benefit one party or group and handicap another. A search of Google provides a wealth of information on this term which entered the American lexicon in 1812, more than a century before the term "geographic information systems" (GIS). Today GIS provides tools that allow political parties to enhance their power and subvert equal representation in ways that were previously impossible. |
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The Pennsylvania Constititution [Article II, Section 16] establishes three conditions for the Commonwealth's senatorial and representative districts. (They) "shall be composed of compact and contiguous territory as nearly equal in population as practicable." These three conditions are applied to congressional districts as well. The last two are met by the new boundaries. "Compactness" or the lack thereof is easy to see (from the maps below) but more difficult to define. |
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The circle is the most compact figure in plane geometry. It has the smallest perimeter for a given area. By analogy, a circular area requires the least amount of fencing to enclose it. Of course, political boundaries are determined by history and physical geography, not geometry. Still, one can use a perimeter to area ratio* to compare geographic units. The table below shows this ratio for some Pennsylvania political units. The larger the ratio, the more disperse the unit. |
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*Notes: The actual formula is perimeter/sqrt(area) which cancels the units yet maintains the meaning of the metric. Our base unit was the meter. We calculated the table using decimal degrees which are native to the spatial data we used and the means were about 1% higher with the same standard deviations. It is revealing that PA counties and municipalities are close in compactness and that Congressional boundaries do not reflect that structure. It is clear that the GOP gerrymander is even more disperse and does not reflect the State's basic political units. |
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Measuring a Gerrymander |
Comparison Maps |
The NE PA Story |
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