How is Leverage Index defined?

[longbomb]

the Bullpen guide is promoting the metric of Leverage Index, but I couldn't find it's definition. What is it?

[RAY@HQ]

Yeah, we should have a definition somewhere more prominent. Here it is:

On February 11, this column introduced some usage indicators that are new to BaseballHQ.com that can be found in the Team Bullpen Indicators chart. The most important of the four columns in this table under "usage" is "Leverage Index." Leverage Index ("LI") was developed by Tom Tango or his associates at tangotiger.net. LI measures the amount of swing in the possible change in win probability indexed against an average value of 1.00. Thus, relievers who come into games in various situations create a composite score and if that average score is higher than 1.00, then their manager is showing enough confidence in them to try to win games with them. If the average score is below 1.00, then the manager is using them, but not showing nearly as much confidence that they can win games.