NFL Penalty Analysis, Referee Influence and Penalty Trends Over Time

One of the biggest determinants of how American football is played are the rules which dictate what actions within the game are legal. Violations result in penalties of varying degrees, which can significantly impact the course of a game. This thesis examines NFL penalties over the last twenty years, focusing on understanding the effect of individual referees and home-field bias, changes in penalties over time, and the differences between NFL teams’ penalties. While a statistical analysis did not find evidence supporting individual referee bias, there was a significant decrease in penalties for the years 2005 through 2008. Additionally, there was a consistent and significant difference in penalties by team, with the Las Vegas Raiders, Baltimore Ravens, and Los Angeles Rams as the most-penalized teams, and the New York Jets and Indianapolis Colts as the least-penalized. Overall, the findings suggest structural explanations for penalty trends, such as major rule changes and organizational culture, rather than individual referee influence.