The Bipartisan Index - Frequently Asked Questions

Who is the author of the Bipartisan Index?

The Bipartisan Index is a joint project of The Lugar Center and the McCourt School of Public Policy at Georgetown University.

What does the Bipartisan Index measure?

In the most general terms, the Bipartisan Index measures: 1) the frequency with which a member of Congress sponsors bills that are co-sponsored by at least one member of the opposing party; and 2) the frequency with which a member co-sponsors bills introduced by members of the opposite Party.  These two components contribute equally to a member’s overall score.  On the sponsorship side of the formula, members also derive some credit for sponsoring bills with greater numbers of bipartisan co-sponsors.

Why did you create the Bipartisan Index?

There are innumerable studies, rankings, and indexes that grade members according to a partisan, parochial, or special-interest standard.  There also are vote studies that rank members from most conservative to most liberal.  We sought to develop an objective measure of Congress’ activity that would focus on bipartisanship, rather than where members sit on an ideological spectrum.  We start from the premise that bipartisanship is not centrism.  Members at the opposite ends of the political spectrum can function in a bipartisan manner if they recognize the importance of building a consensus for their ideas and if they are open to at least considering the proposals of the other party. 

Why does your Index focus on bill sponsorships and co-sponsorships?

First, they allow for a highly objective measure of a member’s proclivities for working across the aisle.  Second, sponsorships and co-sponsorships are carefully considered decisions that stake out long-term positions.   As such, they are less affected by short-term context and are especially reflective of a member’s thinking. Decisions on many votes, for example, are affected by procedural context.  Vote studies generally rely on some degree of subjective analysis.  That being said, we welcome studies of cross-party interaction and bipartisanship that focus on votes or other measures.

How should we interpret the actual number score of each Member?

Majority and minority members are compared to the average score of their respective groups over a 20-year baseline period that includes the 103^rd through the 112^th Congress (1993-2012).  A positive score (a score above 0.00) indicates that a member has scored better on the Bipartisan Index formula than the average score for members of their respective group during that 20-year baseline period.  A negative score indicates that a member falls below the average of their group for the 20-year baseline period.  Scores above 1.0 are outstanding.  Scores above .5 are very good.  Conversely, scores below -.5 are poor.  Scores below -1.0 are very poor.

Why does the Bipartisan Index compare minority members to a historical standard for minority members and majority members to a historical standard of majority members, rather than just comparing how many bipartisan co-sponsorships and sponsorships each member has, regardless of their majority and minority status?

Members of the majority and minority behave differently with regard to sponsoring and co-sponsoring bills.  This is true historically, regardless of which party is in the majority.  Minority members are more likely to be co-sponsors of the other party’s bills because of the majority’s role in proposing legislation and chairing Committees. To overcome this bias and to establish a useful historical baseline, members are compared to the performance of members in similar circumstances to their own over a lengthy period of time.

What is your source of data?

Our raw data comes from GovTrack, which we recommend to anyone who wants to study or follow Congress closely.

Are all bills included in the Index?  Does the Index select some legislation and exclude others?

The Bipartisan Index does not subjectively select bills to “grade.”  There is no weighting of bills.  However, the Index is focused on measuring actions related to substantive legislation.  Therefore, it includes only “S” bills and “HR” bills.  It does not include resolutions.   Through a computer program, we also eliminate private relief bills, commemorative coin bills and post office naming bills even though they have the “S” and “HR” designations.

Are all members given individual scores?

Almost all.  We exclude a small number of members who fit into one of three categories.  First, we exclude members who have served partial terms of less than 10 months of a full Congress (or less than six months if scores are for a single year, such as 2015), because they often do not have a sufficiently large body of legislative work to offer a valid comparison.  Second, we do not score the Speaker and Minority Leader of the House or the Majority and Minority Leaders of the Senate, because their roles in the legislative process impose on them different sponsorship and co-sponsorship practices than other members.  We believe that their level of bipartisanship should be judged by other criteria.  Third, beginning with the 113th Congress, we exclude members who have sponsored fewer than three qualifying bills over the course of a full Congress.  This exclusion applies primarily to the House of Representatives, because it is rare for a Senator serving more than 10 months of a Congress to sponsor fewer than three bills.

Are Bipartisan Index scores in one chamber affected by what happens in the other chamber?

No.  Senate members are compared to the 20-year historical average of the Senate.  House members are compared to the 20-year historical average of the House.  The House and the Senate are different institutions with different rules and practices that affect sponsorship and co-sponsorship activity.  Although the Bipartisan Index formula is the same for both houses, the data is entirely segregated. House scores are not changed by what happens in the Senate and Senate scores are not moved by actions in the House.  It is possible for trend lines in the two chambers to go in opposite directions over time.

Are single year scores, such as those from 2015, comparable to scores covering a full Congress?

They are not perfectly equivalent.  We consider scores for the first year of a Congress, such as 2015, to be “interim” scores.  They offer a valid comparison between members who served that year.  Bipartisan Index scores for the first year of a Congress, however, tend to be slightly lower than those achieved during a full Congress.  Primarily this is because two of the Index metrics (total bipartisan co-sponsorships and total bipartisan sponsorships) improve with any additions during the second year of a Congress.   Those metrics can only decline in the rare cases where members withdraw support for a bill they have sponsored or co-sponsored.  Of course, a Member’s score can decline in the second year of a Congress if his or her percentage-based metrics decline.  See Methodology for an explanation of Index metrics.

Can a member who scores poorly on the Bipartisan Index be considered bipartisan?

A member of Congress may make the argument that he or she expresses their bipartisanship in other ways, such as maintaining their civility in debate, cooperating on Committee hearings and initiatives, or even voting for a significant number of the other party’s proposals. But a very negative score on the Bipartisan Index indicates that a member is giving little thought to working with the other party when he or she introduces bills and makes co-sponsorship decisions.  These are fundamental legislative indicators.

What do you hope to achieve?

First, we want to give the public an objective tool with which they can measure how frequently their members of Congress are cooperating with the other party on matters of policy.  Second, we hope to incentivize members of Congress to be more bipartisan when they write bills and make co-sponsorship decisions.  We hope that they will work to improve their scores by involving members of the other party when they write bills and by having an open mind toward the bills introduced by the other party.  

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