🏈 The 1931 NFL season

Elo moves after every game by the margin and by how surprising the result was, so a rating is a running answer to “how good is this team right now” rather than a summary written at the end. Every league that ran in a season is rated in ONE pool, so the 1946-49 AAFC and the 1960-69 AFL are rated against the NFL of their day; only the standings below are split. A bye or a week after elimination inherits the previous rating and is drawn dashed, because it is a held value and not a fresh measurement.

The record is the final regular-season record. The strip on each row fills in from the left as a team went further: playoffs, division, best record in its conference, conference final, championship game, championship. An asterisk on a record is the best record in the league, and a seed is the number a team carried into the playoffs. Teams level on record are ordered by the NFL tiebreaking procedure, applied to the results as they stood after each week: head-to-head, division and conference records, common games, strength of victory and schedule, points rankings and net points, in the order the league used that season. Scrub to any week and the seed column shows where each team would have been seeded had the season ended there. The playoff and title columns are odds, not records: after each week the games so far are as played and the rest of the season is drawn 2,000 times from the Elo ratings of that week (65 points to a home side), each drawn season seeded by the tiebreaking procedure and played through the bracket of the era; the title is the league championship to 1965 and the Super Bowl from 1966. "clinched" and "out" appear only where the records alone settle it, allowing for who still plays whom; a clinch that rests on a tiebreaker shows as a number, and a small number is not an elimination.

One row per regular-season week, stacked bottom to top from week 1 so every team's column is the same height and lines up on the same week axis; above the seam, one row per playoff round the season had, so the champion's column runs all the way up and a team that went home in the wild-card round stops there. A box's colour is win or loss; its shade is how surprising the result was, from the probability the model gave the side that actually won, banded into expected (60% or better), toss-up, and shock (under 40%, which also gets an outline and a corner dot so it still reads without colour). A bye, in the season or as a seeded rest, is an empty dashed slot; a tie is a thin grey box; a blank slot above the line is a season already over. The label under each column is the team's abbreviation in that season, so the 1999 Rams read STL. Teams are ordered by regular-season wins.

Computed from the results as they stood after each week with the tiebreaking procedure of that era (head-to-head, division and conference records, net points; common games from 1980; strength of victory and schedule and the points rankings from 2002), so the number is a position, not a forecast. E and W are East and West; CAP, CEN, CST and CTR are the 1967-69 Capitol, Century, Coastal and Central divisions. Until 1966 in the NFL and to the end in the AFL a tied division title was played off, so clubs level on the record after a week are all shown, starred, and the PO column carries the playoff that settled it: the winner filled, the loser struck through. The NFL used tiebreakers from 1967. Where a league took two clubs from each division (the 1969 AFL) the cell shows the division rank, which fixed the pairing; a single group (the 1949 AAFC) keeps its rank. Rows are the final order; the line is the cut. The scrubber above highlights its week here. In 4 weeks two clubs were level on every step the ledger can score and the club first by name was placed first; the raw file lists them.

Game Score is built from the two ratings going in, how close the result was, what was at stake and how far the winner was from being favourite, so a tight upset in a Super Bowl scores above a blowout in week 3 without anyone deciding it should. The same measure ranks the all-time board on the NFL hub.

A team can gain a lot and still miss the playoffs, and a team can win its division while the model thinks less of it in January than it did in August. That gap is the season's real story and no final table contains it.

The rating on this page is a description of what happened. Turning it into a probability BEFORE a game and then grading that probability is a different and much harder claim, and it is the one the game log makes. The comparison is against the closing betting line, which is the number to beat, and mostly it wins.