Testing The Conventional Wisdom On NBA Overtime

A statistical analysis.

By
Jake Levy
by Jake Levy

BuzzFeed Data Scientist

A few assumptions are often tossed around about overtime: first, that the home team has an advantage; and second, that teams carry over fourth quarter momentum into extra time. We looked at both, breaking down how often the home and away teams won in a variety of scenarios.

The data used in the analysis comes from SportsDataBase.com and covers all games from the 2002-03 season up to the beginning of the 2013 playoffs (a total of 754 overtime games).

The graphic above displays historic results for both home and away teams under nine different overtime scenarios. The vertical columns tell you which team had the better record going into the game — the "tie" column means they had the same record coming in. The horizontal rows list which team was winning the game going into the fourth quarter of regulation.

The two bars in the upper left corner of the chart, for example, are the results of games in which the home team had a better record than the visitor and led the game at the start of the fourth quarter. (In other words, the away team staged a comeback to force overtime.)

A few general results of the analysis:

Away teams who'd blown a lead did better than away teams who'd made a comeback.

Specifically, away teams that came into the game with a better record than their opponents won more overtimes after LOSING a fourth quarter lead than they did after making a fourth quarter comeback, suggesting that momentum isn't all it's cracked up to be. (Away teams that had worse records than their opponents did about the same in overtime whether or not they'd lost a lead.)

Overall, home teams won fewer overtime games than they did games as a whole.

Home teams won 61% of ALL games in the time period studied but only 54% of those that went to OT, which means our results might suggest that home-court advantage isn't as important in the extra period as conventional wisdom would have it. (Of course, visiting teams that force overtime are probably better on the whole than the general pool of all visiting teams.)

And the team with the better record won 59% of the time.

Makes sense. They were the better team.

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