by Jerry Tsai
The scoring performance of a National Football League (NFL) placekicker can be (and has many times been) a major factor in a team’s success. By kicking field goals and point-after-touchdowns, NFL placekickers directly score about one-third of their team’s points. For example, in the 2007 regular season they were directly responsible for 3,550 of the 11,104 (32.0%) points scored. Morrison and Kalwani (1993) analyzed the performance of NFL-level placekickers and suggested that variation in their collective performances could be ascribed more to luck— binomial variance— than to large differences in ability. Slight differences in ability, however, could have a discernible effect on a team’s success, because during the course of a season, placekickers have many opportunities to increase their team’s score. In the last five regular seasons spanning 2003 through 2007, placekickers averaged 3.7 field goal attempts and 4.5 point-after-touchdown attempts (thus 8.2 scoring opportunities) per game, and each team averaged more than sixty field goal and point-after-touchdowns attempts per season. Play-by-play data from the five most recent seasons were culled to yield information that affect the scoring performance of placekickers, including the physical variables of distance, venue, precipitation, field surface, temperature, and wind speed. Also constructed were variables indicating whether kicks were made under pressure, using time remaining in the game, score differential, and whether a timeout was called to “ice” the kicker. A hierarchical model was constructed and posterior distributions obtained for individual placekickers suggest who was best in the past five years.