The GeoDemographics of Gerrymandering

Article 1, Section 2 of the U.S. Constitution lays out the basis for the census in the U.S. The enumeration of the population (all persons counted equally--as modified later by the 14th amendment) is the basis for dividing up states into Congressional Districts from which members of the House of Representatives are elected. Each such district is to have equal numbers of people, with the exception that each state must have at least one Representative in Congress. Since the Constitution says nothing more about how to create these districts than that cannot cross state lines, the district boundaries have been regularly messed with, starting way back in 1812 when Elbridge Gerry, then governor of Massachusetts, approved a salamander-shaped district, and thus was born the term "Gerrymandering."

While race was the big issue for most of U.S. history, over the past decade the Republican party, in particular, has been trying to redraw Congressional District boundaries in ways that are aimed at providing safe seats for Republican members of Congress. Today's CBS Sunday Morning has a nice primer on the whole set of issues.

Federal judges this past week ordered a redrawing of the lines between Congressional Districts in North Carolina, while the Supreme Court agreed to hear an appeal of a similar ruling in Texas. And then there's Pennsylvania -- which features a Congressional map that, some critics say, looks like a cartoon. [see map below]

But -- and this is important -- even if lines were not being drawn to favor Republicans, Democrats would still be at something of a disadvantage, says Stanford political scientist Jonathan Rodden. That's because of where they live.

"Democrats have been clustered in cities in the industrialized states every since the New Deal, ever since FDR," Rodden said. "Cities have become more Democratic, and rural areas more Republican." 

Rodden studies how increasingly Republicans are spread across rural areas and Democrats packed into urban areas. Consider the influence on a state like Missouri: "The Democrats are highly concentrated in St. Louis and Kansas City," Rodden said. "The gubernatorial elections are always very close. It's a place that Democrats can win statewide. But the best they can hope for in an eight-seat Congressional delegation is three seats, and the current outcome is two." 

So, is the issue gerrymandering or geography? "It's geography and gerrymandering," said Rodden. "In order to understand the outcomes we see, we have to understand how those two things interact."

Strictly speaking, of course, it's not just geography--it's GeoDemographics or spatial demography at work in a big and important way.