The Republican candidate for the US House of Representatives from Maryland’s 6th Congressional District, the westernmost district in the state, conceded the election to the Democratic incumbent today, the Baltimore Sun reports.
The race turned out as expected, except for being as close as it was. The western part of Maryland tends to the Republican side on most issues, but gerrymandering has kept enough Democratic votes in the district to advance the careers of Democrats.
Dan Bongino, the Republican candidate, praised Rep John Delaney in his concession, mainly on personal grounds, as the Democratic congressman had inquired about Mr Bongino’s wife during the campaign. She had become ill in the middle of the race.
“It reminded me that although our wonderful country is currently marked by passionate political differences, these differences should never become personal,” the Sun quoted Mr Bongino as saying. “The artificial divisions in our country created by those interested in stirring emotions today, rather than fixing tomorrow, are the only enemy that stands a chance at dismantling what we have created here.”
Some complaints of gerrymandering in Maryland
I suppose how much gerrymandering you think there is in any given state depends on which party won the election where you live. But Marylanders sure heard a lot about gerrymandering during the recent election (also see here and here).
It may surprise you to know there’s a mathematical way to compute the degree to which Congressional districts are gerrymandered within a state. Consider the perfect situation, where every district is a perfect circle. There would be no gerrymandering in this case.
One important fact about circles, from a geometric perspective, is that they represent the shape that covers the most area while having the lowest perimeter. The degree to which the district outlines in a state have a low perimeter compared to their area, therefore, can be used to compute a numerical value that represents the degree to which each district in a state is gerrymandered. The average of those values for a state could then be used to model the degree to which the state has gerrymandered districts. Mathematically,
where G is the gerrymandering index (higher values represent districts that are less gerrymandered), a represents the area of the district, and p represents the perimeter of a district.
Now we need a formula to compute a number. We want the numerical value to be 100 if every district were a perfect circle and 0 if every district were gerrymandered to infinity. The formula also needs to consider the relationship between perimeter and area in a perfect circle. How about this one, suggested on the site GeoIdeas.net:
That has us multiplying 100 by a number that asymptotically approaches 0 as the perimeter goes to infinity and 1 as the dimensions of the district resemble a perfect circle, in which 4aπ divided by the perimeter squared would be 1. That will give us a number from 0 to 100.
Another important fact about circles: They don’t overlap perfectly if every square mile of ground is covered, meaning a state’s average can’t be 100, since there’s no way every Congressional district in a state could be a perfect circle.
For a perfect circle, the area = πr2. Then, since the perimeter = 2πr, we have
We can use the expression we do to compute the gerrymandering index simply because as the shape of a district approaches a perfect circle,
Due to the meandering coast in Chesapeake Bay, Maryland’s gerrymandering index of 7.39 is a little worse than the national average of 14.19. The Congressional disttricts themselves, however, are close to the average for the entire country. You may be able to make small adjustments to the model to account for the Chesapeake Bay’s many estuaries.
Alaska and North Dakota each have one Congressional district, but Alaska’s gerrymandering index is much lower. Why is that? See Common Core modeling with geometry standard HSG.MG.A.3 for more information.
