> Second, we compute the efficiency gap for congressional and state house plans between 1972 and 2012. Over this period as a whole, the typical plan was fairly

> Second, we compute the efficiency gap for congressional and state house plans between 1972 and 2012. Over this period as a whole, the typical plan was fairly balanced and neither party enjoyed a systematic advantage. But in recent years — and peaking in the 2012 election — plans have exhibited steadily larger and more pro-Republican gaps. I think the way we normally talk about gerrymandering as a tool that one party uses to gain an electoral advantage over another party is kind of misleading and may lead us to measure success by the wrong metric. Another way to thing about gerrymandering is not as a Republican vs Democrat thing, but an elected officials versus their constituents thing. To use the US House of Representatives as an example, House members of both parties want the same thing, which is to get re-elected. Furthermore, they want to be re-elected by such a wide margin that their job is secure and they don't have to spend a lot of time and effort campaigning. The voters, on the other hand, want their elected representatives to be accountable, and so they want them to be afraid of possibly losing the next election. Voters want their preferred party/candidate to win, but it's also in their best interests that elections are close enough that the implicit threat of withholding their vote is enough to motivate their representative to do their job well (whatever that means to the voter). When party A is able to re-arrange their districts so that all their candidates have safe seats, they usually cram a bunch of party B's supporters into districts that also give a certain (smaller) number of safe seats to party B. If you think of this as a zero-sum game between party A and party B, then party A wins a certain number of seats and party B loses an equal number. If you think of this as a game between the voters and their Representatives, then the Representatives (of both parties, except for the handful in party B that lose their seats) won because fewer of them have to work to get votes and the voters lost because they have less influence than they did before. The efficiency gap seems like a good metric to measure whether party A or party B is winning, but it's not obvious to me that it's a good metric for measuring how safe the seats in a given state have become. The efficiency gap metric would say that 50% of the votes were wasted in a 2-way near-tie for a not-safe seat, but also that 50% of the votes were wasted in an election for a safe seat if one candidate got 100% and the other got 0%. I'm not sure how best to measure seat safeness in a way that can distinguish an unbalanced result due to gerrymandering versus an unbalanced result due to one candidate running a better campaign than his/her opponent. We can look at margin-of-victory statistics in many races in many districts and make generalizations about how there are more safe districts now than some time in the past, but it's harder to say conclusively (in a way that would persuade a judge) that one particular district is gerrymandered.