Legislative Seriousness Index
The Legislative Signal Index (LSI)
Most bills introduced in Congress never become law. Many are symbolic, rhetorical, or tactical — designed to make a point, not policy. Others have a credible path forward but get lost in the noise. The Legislative Signal Index (LSI) is an attempt to measure that difference objectively.
What the LSI Measures
The LSI is a non-normative indicator of a bill’s structural viability — how far it’s likely to advance based on measurable signals of institutional momentum rather than its content or perceived merit.
These signals include factors such as:
• Sponsorship dynamics – number and diversity of cosponsors, including cross-party support.
• Procedural traction – committee assignments, hearings held, and movement through legislative stages.
• Contextual momentum – similarity to prior bills that reached the floor or became law.
• Institutional cues – alignment with leadership priorities or procedural fast-tracking.
Why It Exists
The goal isn’t to predict outcomes with moral judgment or policy bias. It’s to separate legislative signal from political noise — highlighting which bills are likely to matter procedurally in the coming months.
In that sense, LSI is less a political forecast than a measure of institutional seriousness.
How to Read It
An LSI score closer to 100 indicates a bill with strong procedural momentum and historical analogs suggesting passage potential.
A score near 0 reflects a measure that exists mainly as a statement of position — important politically, but not legislatively.
Member Mean LSI
When it comes to member "Mean LSI" ratings, this unsurprisingly is the mean of all the bills sponsored by the member. It measures the "signal" from a member, indicating how often the member's bills make it significantly through the legislative process. Again, this is not to render judgment on the worth of a member one way or the other, but it does indicate to what degree the member is involved in legislation that will have more than a rhetorical effect.
Where to go from here
- Top Bills - The top highest LSI score bills that have not been enacted yet.
- Top Legislators - The top legislators by adjusted Mean LSI
- Bottom Legislators - The bottom legislators by adjusted Mean LSI
The "adjusted Mean LSI" is just adjusted to account for relatively inactive members in terms of sponsorship.