This is a measurement of the importance of a particular game, based on how a win or a loss affects a team's World Series win expectancy.
A CLI of 1 is equal to the importance of the average game on opening day. In the 2nd Wild Card era, the difference between a win and a loss on opening day affecting World Series win expectancy is about .059 percentage points. A CLI greater than 1 would indicate that the particular game is more important than the average game on opening day, while a CLI less than 1 indicates it is less important.
World Series win expectancy in the 2nd Wild Card era is calculated as: (division win expectancy / 8) + (wildcard win expectancy / 16).
If a team has already been eliminated from postseason contention, they have a 0% World Series win expectancy. A win would not increase this number since they are already eliminated, giving them a CLI of 0 for the remainder of their games. The same goes for a team that has already clinched their division. A division championship means that a team is one of the 8 teams in the postseason tournament, giving them a 12.5% (1 / 8) World Series win expectancy. If this team were to lose their next regular season game, their World Series win expectancy will not go down since they have already clinched their division. So their CLI would also be 0.
CLI is calculated by twice simulating the remainder of the season 50,000 times. The first time to figure out the World Series win expectancy if that team were to win their next game, while the second time is for if that team were to lose their next game. The difference between these two numbers is then divided by .059, giving us the team's Championship Leverage Index for that game.
Championship Leverage Index is also used for postseason games
. In this case, a CLI of 1 is equal to the importance of Game 1 of the World Series. This is done because the importance of the average game on opening day of the regular season has changed over the course of baseball history. The expansion from 16 to 30 teams and the addition of extra playoff teams has affected how World Series win expectancies change during an individual regular season game.
Therefore, CLI's for regular season games and postseason games should not be compared. A postseason game with a CLI of 1.25 is FAR more important than a regular season game with a CLI of 1.25