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We introduce the Geography and Election Outcome (GEO) metric, a new method for identifying potential partisan gerrymanders. In contrast with currently popular methods, the GEO metric uses both geographic information about a districting plan as well as district-level partisan data, rather than just one or the other. We motivate and define the GEO metric, which gives a count (a non-negative integer) to each political party. The count indicates the number of previously lost districts which that party potentially could have had a 50% chance of winning, without risking any currently won districts, by making reasonable changes to the input map. We then analyze GEO metric scores for each party in several recent elections. We show that this relatively easy to understand and compute metric can encapsulate the results from more elaborate analyses. [ABSTRACT FROM AUTHOR]

We explore the Declination δ, a new metric intended to detect partisan gerrymandering. We show that when vote share is fixed, δ = 0 allows for a wide array of possible seat shares, even when turnout in each district is equal. In particular, if δ = 0, the majority party has higher seat share when its average vote share in districts that it wins is closer to the statewide vote share. This range of possible seat shares with δ = 0 results in a range of responsiveness, again depending on the average vote share in districts won by the majority party. We also prove what kind of vote-share seat-share pairs can result in δ = 0 when the maximum district turnout to minimum district turnout is bounded, and turnout is unrestricted. Within our analyses, we show that Declination cannot detect all forms of packing and cracking, and we compare the Declination to the Efficiency Gap. We show that these two metrics can behave quite differently, and give explicit examples of that occurring, including examples from recent election data. [ABSTRACT FROM AUTHOR]