What is the Cook PVI℠?

The Cook PVI measures how partisan a district or a state is compared to the nation as a whole.

What do the scores mean?

A Cook PVI score of D+2, for example, means that in the 2016 and 2020 presidential elections, that district performed an average of two points more Democratic than the nation did as a whole, while an R+4 means the district performed four points more Republican.

How is the Cook PVI different from race ratings?

Whereas race ratings reflect our outlook for which party will win the next election in each state and district, PVI values take a longer view and seek to measure the underlying partisanship of each district relative to the nation as a whole.

Historical Cook PVI℠ Values Now Available

For more than 25 years, the Cook Partisan Voting Index (Cook PVI℠) has served as a useful metric to compare the partisan leanings of all 435 House seats and 50 states. Today, we're publishing historical PVI values for every set of congressional districts dating back to 1997 — all in one place.
1997

2023 Cook PVI (118th Congress)

The 2023 Cook PVI scores were calculated following the 2021 round of redistricting, using 2016 and 2020 presidential election results. They are identical to the PVI scores released in 2022.

2021 Cook PVI (117th Congress)

The 2021 Cook PVI scores were calculated using 2016 and 2020 presidential election results. They also reflect court-ordered changes to district boundaries in North Carolina prior to the 2020 election.

2019 Cook PVI (116th Congress)

The 2019 Cook PVI scores were calculated using 2012 and 2016 presidential election results, updated to reflect court-ordered changes to district boundaries in Pennsylvania prior to the 2018 election.

2017 Cook PVI (115th Congress)

The 2017 Cook PVI scores were calculated using 2012 and 2016 presidential election results. They also reflect court-ordered changes to district boundaries in Florida, North Carolina and Virginia prior to the 2016 election.

2015 Cook PVI (114th Congress)

The 2015 Cook PVI scores were calculated using 2008 and 2012 presidential election results. They are identical to the PVI scores from the previous Congress.

2013 Cook PVI (113th Congress)

The 2013 Cook PVI scores were calculated using 2008 and 2012 presidential election results.

2012 Cook PVI (Post-Redistricting)

The 2012 Cook PVI scores were calculated following the 2011 round of redistricting, using 2004 and 2008 presidential election results. They reflect the new district lines then set to take effect for the 113th Congress, but do not reflect the 2012 presiden

2011 Cook PVI (112th Congress)

The 2011 Cook PVI scores were calculated using 2004 and 2008 presidential election results. They are identical to the PVI scores from the previous Congress.

2009 Cook PVI (111th Congress)

The 2009 Cook PVI scores were calculated using 2004 and 2008 presidential election results.

2007 Cook PVI (110th Congress)

The Cook 2007 PVI scores were calculated using 2000 and 2004 presidential election results, updated to reflect Republican-passed changes to district boundaries in Georgia and court-ordered changes to district boundaries in Texas prior to the 2006 election

2005 Cook PVI (109th Congress)

The 2009 Cook PVI scores were calculated using 2004 and 2008 presidential election results.

2003 Cook PVI (108th Congress)

The 2003 Cook PVI scores were calculated following the 2001 round of redistricting, using only 2000 presidential election results as 1996 results were not available for the newly redrawn congressional districts.

2001 Cook PVI (107th Congress)

The 2001 Cook PVI scores were calculated using 1996 and 2000 presidential election results. They also reflect court-ordered changes to district boundaries in North Carolina prior to the 2020 election.

1999 Cook PVI (106th Congress)

The 1999 Cook PVI scores were calculated using 1992 and 1996 presidential election results, updated to reflect court-ordered changes to district boundaries in North Carolina and Virginia prior to the 1998 election.

1997 Cook PVI (105th Congress)

The 1997 Cook PVI scores were calculated using 1992 and 1996 presidential election results.

2022 Cook PVI: 25th Anniversary Edition

Now that all 50 states have finalized new lines for the 2022 elections, the Cook Political Report is pleased to introduce the 25th Anniversary edition of the Cook Partisan Voting Index (Cook PVI℠) for all 50 states and 435 congressional districts, reflecting new post-redistricting boundaries. First introduced in 1997, the Cook PVI measures how each state and district performs at the presidential level compared to the nation as a whole.
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The Cook Partisan Voting Index (Cook PVI℠) Explained

In August of 1997, The Cook Political Report introduced the Cook Partisan Voting Index (Cook PVI) as a means of providing a more accurate picture of the competitiveness of each of the 435 congressional districts. Whereas our race ratings reflect our outlook for which party will win the next election in each state and district, the Cook PVI takes a longer view and seeks to measure the underlying partisanship of each district relative to the nation as a whole.


We have released new PVI scores following every election and instance of redistricting since 1996, each time taking into account the prior two presidential elections. Prior to 2020, the Cook Political Report contracted with Clark Bensen's firm Polidata to calculate presidential results by congressional districts and PVI scores. In 2021, the Cook Political Report teamed up with Dave Leip's Atlas of U.S. Presidential Elections to calculate 2020's results by district.

This time, to calculate new PVI scores for all 435 newly drawn districts, we've used 2016 and 2020 election results by district publicly available via Dave's Redistricting App, a free online mapping tool originally developed by Dave Bradlee that allows any user to draw and evaluate district boundaries. The app uses precinct-level election data largely compiled by the Voting Election & Science Team (VEST), a consortium of academic researchers.

The Cook Partisan Voting Index is an attempt to find an objective measurement of each congressional district and state. While other data such as the results of senatorial, gubernatorial, congressional and other local races can help fine-tune the exact partisan tilt of a particular district, those kinds of results don’t allow a comparison of districts across state lines. Only presidential results allow for total comparability.

A Partisan Voting Index (PVI) score of D+2, for example, means that in the 2016 and 2020 presidential elections, the state or district performed about two points more Democratic in terms of two-party vote share than the nation did as a whole, while a score of R+4 means the state or district performed about four points more Republican. If a state or district performed within half a point of the nation in either direction, we assign it a score of EVEN.

To determine the "national value" for these latest Cook PVI scores, we've taken a weighted (75/25) average of the Democratic share of the two-party presidential vote in 2020 and 2016, which is roughly 51.98 percent. So, if Joe Biden and Hillary Clinton both carried 57% of the vote in a given district in 2016 and 2020 respectively, the district would have a PVI score of roughly D+5. If they only carried 48%, the district would have a PVI score of R+4.

COOK PVI℠ is a service mark of Invincible Summer Media, Inc.