In August of 1997, the Cook Political Report introduced the Cook Partisan Voting Index (Cook PVI) to provide a more accurate picture of the competitiveness of each of the 435 congressional districts. With the 202 PVI release, we made a slight change to how we calculate PVI scores: instead of using a 50/50 mix of the two most recent presidential elections to assess partisanship as we had done in the past, we switched to a 75/25 weighting in favor of the more recent presidential cycle. Using the updated formula, we are now re-releasing PVI scores for every Congress since the 105th (1997-1998).

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Active CPR subscribers can request the Cook PVI data in spreadsheet format.


Map shapefile: Jeffrey B. Lewis, Brandon DeVine, Lincoln Pitcher, and Kenneth C. Martis. (2013) Digital Boundary Definitions of United States Congressional Districts, 1789-2012. Retrieved from on March 25, 2023.

Presidential election data: Before 2020, the Cook Political Report contracted with Clark Bensen's firm Polidata to calculate presidential results by congressional districts and PVI scores.

The content of the Cook PVI is confidential and proprietary to The Cook Political Report, and its expression is protected by copyright. You may use the Cook PVI only for your own lawful, internal purposes and uses (e.g., to inform your own analysis and activities, but not as a stand-alone product apart from your own work). Please give credit to The Cook Political Report where you reference all or a meaningful part of the Cook PVI, and not alter or delete any proprietary legends contained on or in it. Whenever possible, please link the reference back to

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