Gerrymandering

Gerrymandering is the practice of drawing political boundaries—especially the boundaries of legislative districts—in such a way as to obtain political advantage. The term derives from the claim of critics that a legislative district drawn by supporters of Massachusetts Governor Elbridge Gerry in 1812 was shaped like a salamander, or “Gerry-mander.”

Consider the hypothetical region shown in Figure 1, with supporters of party A indicated by the light squares and supporters of party B by the dark squares. In proportional voting systems, the fact that 22/36 of the voters support party A would mean that party A would get that proportion—22/36—of the representation. But in a winner-take-all voting system (as in the United States), the region must be divided into a fixed number of single-winner districts. Assume that by virtue of its population, the region is entitled to three legislators, and hence the region must be divided into three legislative districts.

If the district lines are drawn as in Figure 2, then party B will win two out of the three districts (because it has a majority of the votes in each of the two lower districts, while party A has all the votes in the upper district). On the other hand, if the district lines are drawn as in Figure 3, then party A will win two out of the three districts (the top two districts). And if they are drawn as in Figure 4, then party A will carry all three districts. Thus, whoever gets to draw the lines can maximize partisan advantage.

Different district lines yield different political outcomes because, under winner-take-all voting, a party wins a district whether it has a large majority (with many wasted votes) or a narrow majority. So by arranging for one's own party to win its districts as narrowly as possible and for one's opponents to win their districts with as many wasted votes as possible, one can maximize the number of districts won. (Of course, a party might not want to make its winning edge too narrow, lest a shift in voter sentiment lead to an electoral loss.) With modern computer technology and detailed voter databases, it is possible to manipulate political boundaries with great precision.

Figure 1 Region With Supporters of Party A (Light

Note: Each square represents 100,000 voters.

Several mathematical procedures exist for neutrally drawing district lines—for example, the shortest split-line algorithm. However, it is sometimes thought desirable to have a district made up of people sharing a community of interest (say, living in the same municipality or county, or on the same side of a mountain), factors that cannot readily be accounted for mathematically. Once discretion is allowed, the opportunity exists for manipulation to suit partisan interest.

In Canada and Britain, independent commissions draw the electoral boundaries. In most U.S. states, the state legislatures—which are partisan bodies—draw the congressional district lines. In a few states, a nonpartisan or bipartisan agency—such as Iowa's Legislative Service Bureau, the Washington State Redistricting Commission, and the Arizona Independent Redistricting Commission—is responsible for [Page 406]drawing the lines. Such agencies are often prohibited from considering any demographic data other than population headcount. In some cases these agencies have the last word; in others the state legislature can amend the commission's plan within specified limits.

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