Here, the best team in baseball statistics takes on the only subject that really matters in baseball: Why do teams win pennant races? Statistical analyses of baseball abound: different ways of breaking down batting performance, pitching performance, fielding performance, managerial performance, expected wins and the like. But the one aspect of baseball that, surprisingly, has never been looked at with the same statistical rigour is pennant races. Pennant races are arguably the most important unit in the game. Players, teams and franchises are all after one goal: they all want to win pennant races and get into the post-season. But what really determines who wins? In "It Ain't Over Til It's Over", The Baseball Prospectus Team of Experts first introduces the Davenport Method of deciding which races were the most exciting, the closest, the most volatile, and come up with the ten greatest races of modern baseball history. Some of these are well known - the wild four-team race in the American League in 1967, the Giants' immortal comeback against the Dodgers in 1951, capped by Bobby Thompson's home run - while others, such as the race that never happened in 1981, are less famous than they ought to be. The authors then use these ten key races to analyse aspects of the main question: what determines who wins pennant races? How important are such things as mid-season trades, how much can a manager overwork his pitchers and get away with it, why do teams go on winning and losing streaks? Can one player carry a team? Can one bad players playing consistently ruin a team's chances? Can one bad play ruin a team's chances? This is a fascinating and illuminating look at the one aspect of the game that's received little attention from statisticians. In this follow-up to the successful "Baseball Between the Numbers", the authors will bring their classic approach to a subject that, surprisingly, has not been covered very much.