by Gina Talt
The 2013-14 NBA season is officially underway, and more has changed than just the Brooklyn Nets and Dwight Howard’s jersey. Last week the NBA owners voted unanimously to return to the 2-2-1-1-1 format of the pre-1985 Finals after 29 years of playing under the 2-3-2 format. This change will take place immediately, beginning with the 2014 Finals.
How will the new format affect future Finals series?
According to Commissioner David Stern, the format change reflected a sentiment among the teams in the league that the higher seed was not sufficiently rewarded for its better season record under the old 2-3-2 format. They believed it was unfair for the home team to have to play on the road for a crucial Game 5. Over the last 29 years, the higher seed has been down two games to three after Game 5 nine times. When you take a closer look however, this situation has been a recent trend of late. The higher seed in four of the previous eight Finals and three of the last four Finals has trailed the lower seed after Game 5. While the higher seed had home court advantage in Game 6 and 7, it needed to win both games to come out on top. Yet history shows that the lower seed had a slight advantage at this point. The lower seed ended up with the O’Brien trophy five out of the nine times when it held a one-game lead going into Game 6.
The data seem to back the NBA’s rationale for the change, but how likely was the same scenario under the new 2-2-1-1-1 format which was in place for 28 years before 1985?
With Game 5 at home instead of on the road, there were slightly fewer occurrences (6 compared to 9) when the home team was trailing 2-3. Yet out of those six times the home team only won the Finals once. Testing for statistical significance for either of these differences in proportions between the two formats yielded inconclusive results. The p-value for the difference in occurrences was .41 and .17 for the difference in the Finals outcome. Although the sample sizes were small, these results suggest that both the chance of the higher seed being down 2-3 after Game 5 and the chance of the higher seed clinching the title after winning the last two games are the same under the two formats.
Furthermore, the higher seed has won about the same number of Finals under the 2-2-1-1-1 format (20 out of 28) as the old 2-3-2 format (21 out of 29). This difference is also insignificant with a p-value of .934. A probit model controlling for travelling distance (short if travelling under 1500 miles or about half the country, long if over 1500 miles) and length of series (full series or not) suggests that the marginal effect at the mean of the format change on the higher seed winning was also insignificant with a p-value of .52.
While a return to the old playoff format doesn’t seem to favor the higher seed any more than the 2-3-2 format did based on past results, the 2-2-1-1-1 format may mean an increase in the number of series that reach Game 7. The theory is that a Game 7 will be more likely when Game 6 is played on the lower seed’s home court under the 2-2-1-1-1 format. Indeed, all but two of the full Finals series in the pre-1985 era occurred after the lower seed won Game 6.
For the 28 years that the current format was in place, 10 out of the 28 Finals went seven games, which is twice the number under the 2-3-2 format over almost an identical time period. A t-test for a difference in proportions is insignificant with a p-value of .11. However the difference is significant when testing the probability of a full series occurring against several control dummy variables: travelling distance (defined the same as above) and the seed of the winner. Travelling distance may affect the length of the series by influencing the fan base of the road team and/or the performance of the players. It was the long cross-country commercial flights in the ‘60s and ‘70s that led to the 2-3-2 format change in 1985. Now, travel isn’t as difficult because teams fly their own charters.
The winner’s seed serves as a proxy for the team favored to win (though a more accurate variable would be Vegas odds). The results of a probit regression model show that the marginal effect at the mean of the format change on the series going all seven games is .19 and is significant at the 10% level with a p-value of .096. In other words, a switch from the 2-3-2 format to the 2-2-1-1-1 format yields a 19% increase in probability that the Finals will be a complete seven game series.
Overall, the change to the 2-2-1-1-1 format because it is more “fair” to the higher seed may just be a perceived advantage for the home team rather than an actual one based on the relatively simplistic tests and regressions used in this article. However, these results also show that the new format will surely please fans and the NBA’s TV partners with the likely increase in full series Finals.
Statistics compiled from basketball-reference.com