Same Votes, Different Districts Would Change Results

http://today.duke.edu/2014/10/mathofredistricting

October 29, 2014 | Robin Smith
Duke University

Researchers at Duke University have developed a mathematical model that shows how changes in North Carolina’s congressional voting districts could affect election outcomes.

Focusing on the last election, the researchers varied the state’s congressional districts to calculate what the outcome of the 2012 U.S. House of Representatives elections might have been had the state’s districts been drawn to emphasize nonpartisan boundaries. The team re-ran the election 100 times -- using the same votes as in 2012 and tweaking the voting map with only the legal requirements of a redistricting plan in mind. Not once did they get the split of Democratic and Republican seats seen in the actual election.

The researchers hope the study will bolster calls for redistricting reform in the 2016 election season.

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During the 2012 elections in North Carolina, Republicans took nine of the state’s 13 U.S. House seats although 51 percent of the two-party vote went to Democratic candidates.

The gerrymandering that led to these results isn’t unique to North Carolina or any specific party. Both Democrats and Republicans have used it for political advantage over the years. However, new technology makes it possible to draw partisan districts with increasing precision.

“North Carolina’s 12th and 4th congressional districts in particular look a little crazy,” said study co-author and Duke senior Christy Vaughn, who is originally from Taylorsville, N.C.

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After re-running the election 100 times, with a randomly drawn nonpartisan map each time, the average simulated election result was 7 or 8 U.S. House seats for the Democrats and 5 or 6 for Republicans. The maximum number of Republican seats that emerged from any of the simulations was eight. The actual outcome of the election -- four Democratic representatives and nine Republicans – did not occur in any of the simulations.

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The model isn’t meant as a tool for creating new voting districts, the researchers say.
“Our districts aren’t perfect,” Vaughn said.

But the methods they used can identify when a particular set of district boundaries may misrepresent the will of the people, and quantify the potential effects on an election. “This gives us a way to judge how reasonable a proposed redistricting is and what we should expect under a given set of boundaries,” Mattingly said.

The researchers hope the study will bolster calls for redistricting reform in the 2016 election season in North Carolina and other states. Any changes in the districting process would most likely go into effect after the next national Census in 2020, when states again redraw the boundaries of their congressional maps to reflect changes in their population.