How these are measured
A bill counts for the member who was its chief sponsor last. A shell, a bill introduced to "make a technical change" so that it can be amended into something else later, counts once it has passed a chamber; until then it counts for no one.
Each term's score counts a member's bills at five steps: filed, acted on in committee, out of committee, passed their chamber, and became law. At each step a member's bills are taken as a share of all the chamber's, and the shares are added up, so that the chamber's average member scores 1. This follows the Center for Effective Lawmaking's method in outline. It differs in two ways: it counts every bill alike, where the Center weighs some as more significant than others, and it does not count shells that never moved, which the Center counts as bills.
What was expected of a member is worked out from the members of the same chamber and term: whether they were in the majority, whether they chaired a committee, and how many terms they had served in that chamber, counted from 2017, where l9n's records begin. About as expected is between half and one and a half times that. A term still sitting is scored as it stands that day, and will move.
Across the aisle counts the co-sponsorships between a member and the others in their chamber, those they gave and those their bills drew, and how many were with the other party. Each member is set among their own party, because the minority party crosses more.