Work stoppages are costly to labor and management. One cost of a strike in professional sports is the diminished quality of play that results from missed practices. Some teams and players, especially those with less experience, are harmed more by reductions in practice time. In an earlier blog post I demonstrated that strikes in the NBA are associated with subsequent reductions in the shooting efficiency of players. This post compares the impact of the NFL player lockout of 2011 to the referee lockout of 2012 on NFL game outcomes.
Itis clear to NFL fans that the replacement referees, used in the first two games of 2012, make more imistakes than experienced referees. Although the lockout with referees seems to introduce additional noise into game outcomes, it appears that referee errors are largely uncorrelated with teams’ strengths and weaknesses. In contrast, it appears that the lockout with players favored stronger and more experienced teams.
The player lockout of 2011 drastically reduced the amount of practice time prior to the beginning of the season. One would expect this to have a larger effect on teams with less experienced players and teams that made more roster and coaching changes prior to the season. Successful teams are likely to have greater stability in their personnel, have more experience playing as a team, and are less likely to change offensive or defensive coaching philosophies. Therefore it would not be surprising that a loss in pre-season practice time harmed the weaker teams more than the stronger teams. This is exactly what happened last year. Final score differentials in NFL games were unusually high in the first two weeks of the 2011 season, immediately after the lockout.
In contrast there is less reason to expect that the use of replacement referees during the NFL’s lockout with the more experienced referees would tend to favor stronger or weaker teams. In fact, the final score differentials in the two weeks of the 2012 season are only slightly higher than in earlier seasons despite the use of replacement referees.
The margin of victory in an NFL game includes signals of the opposing teams’ strengths and noise due to luck, player injuries, weather, and other factors. These factors include the impact of a shortened training camp due to the player lockout in 2011 and the use of replacement referees in 2012. The following chart shows the mean absolute score differential for games in the first two weeks of the 2009 through 2012 seasons.The mean score differential was 26% higher early in the 2011 season than it was in the first two weeks of the 2009 and 2010 seasons. Games were more lopsided by about 2.66 points per game in the first two weeks of 2011. If the team most disadvantaged by the shortened preseason always lost the game, the average impact of lost practice time is a 2.66 points advantage for the winning team. If missed practices sometimes worked to the detriment of the winning team the average gross effect on scoring would be somewhat larger. (If the impact of reduced practice time was uncorrelated with team strength the gross impact could be as high as a swing of 5.32 points per game.) It seems likely that shortened practices altered outcomes by at least 3 to 4 points per game and sometimes worked to the disadvantage of the team that ultimately won the game.
In contrast there is a much smaller difference between the average margin of victory/loss between the 2009 and 2010 seasons and the first week of 2012. Although replacement referees have affected the calls on the field, their impact on the typical score differential is only 41% of the increase caused by the players lockout.
Work stoppages and strikes are costly. The 2011 player lockout caused game outcomes to be more uneven. Weaker teams with more rookies and roster changes seemed to be harmed more than successful veteran teams by the lockout of players and loss of practice time. The impact of the strike may have been as high as a swing of 3 to 4 points per game, on average. In contrast the use of replacement referees in 2012 increased final score differentials by much less.