Searching for Momentum in the NFL

We examine the question of whether or not momentum exists in an NFL football game. The concept of momentum is often cited by coaches, players, commentators and fans as a major factor in determining the outcome of the game and, consequently, in-game decision making. To examine the existence of momentum, we analyze particular game situations tied to what we consider to be “momentum-changing plays” (MCPs). These MCPs include fourth down conversions/stops, turnovers and scores allowed. We hypothesize that evidence of positive (negative) momentum would be characterized by increases (decreases) in yards gained, higher (lower) probability of converting a first down and greater (lesser) likelihood of scoring after a positive (negative) MCP. Our data set includes all plays from the 2002 to 2007 NFL seasons. We limit our analysis to game situations where the outcome of the game is still in doubt by removing plays that occur when a team is facing an insurmountable score differential. We use a pairwise matching comparison where we control for the game situations of home/away team, field position, time of game and score differential. We find little evidence for the existence of momentum in these events. Our results are in line with previous papers that find little empirical evidence of momentum in sports. While our findings cannot conclusively disprove the existence of momentum in the NFL, they further support the argument that momentum should not be a guiding factor for in-game decision making.