efficiency gap

politics

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July 22, 2026

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The term "efficiency gap" refers to a metric used in political science to measure the degree of partisan gerrymandering in electoral districts. It quantifies the difference between "wasted" votes for each party. Wasted votes are those cast for a losing candidate or those exceeding the number needed for a winning candidate.1

The efficiency gap is calculated by dividing the difference in wasted votes between two parties by the total votes cast. For example, if Party A wastes 70 votes and Party B wastes 180 votes in a 500-vote election, the efficiency gap is 22% in favor of Party A. A significant efficiency gap can indicate that a redistricting plan unfairly advantages one party, potentially leading to a situation where one party wins a majority of seats despite receiving fewer overall votes. This concept was notably discussed in the legal case Gill v. Whitford concerning Wisconsin's redistricting plan.1

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gerrymandering
…be represented as an “efficiency gap” between the parties when the difference between wasted votes is divided by the total number of votes cast. The plaintiffs argued that efficiency gaps of 7 percent or greater were legally significant because they were more likely than smaller gaps to persist through…
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…be represented as an “efficiency gap” between the parties when the difference between wasted votes is divided by the total number of votes cast. The plaintiffs argued that efficiency gaps of 7 percent or greater were legally significant because they were more likely than smaller gaps to persist through…
Read More