After we wrote about Mike Tomlin's fake field goal decision in Week 9, it got me thinking about the general success rate of fakes versus typical fourth down attempts. Before moving forward, it should be noted that it is difficult to pull fake field goal and fake punts out of play-by-play data because they are not explicitly specified as such. So, you may be getting an aborted or bad snap or the field goal/punt formation may not have been recorded. We attempted to clean the data up as much as possible, which resulted in 213 fourth down fakes since 2000.
Similarly, we looked at the roughly 5500 fourth down normal go-for-it attempts. Granted, a lot of these will take place at the end of the game when teams are down by significant margins or must go for it in order to stay in the game, but that should not greatly affect their conversion rates. It may give us a sample bias, though, because those teams that are losing are typically worse offensively.
Fake attempts are exceedingly rare and given that there are only 200 or so attempts, we must be cautious of sample size issues. The most frequent fake attempts are on 4th-and-1 or 4th-and-2 which have happened about 30 times a piece. Compare that to over 2000 regular go-for-it attempts on 4th-and-1 and over 600 regular attempts on 4th-and-2.
To assess the value of a fake attempt I looked at success rates based on distance-to-go and then used logistic regression to smooth the data. The results:
The blue represents actual fake field goal and punt success rates while the green represents actual go-for-it success rates. The red smoothed line is an estimate of fake success rates while the purple is an estimate of regular fourth down attempts. It is pretty noticeable that fakes convert at a higher rate, especially with 6 or less yards-to-go. That difference gradually reduces as distance-to-go increases.
The main value of a fake is the surprise nature. Opposing defenses (or special teams) are not expecting a team to go for it and as a result, they are caught off guard without proper defenses. One huge thing to note is that fakes are typically employed when the coaching staff notices a trend for not defending against the fake in their opponent. That is, a coach will notice that there is no safety net on a punt whenever a team defends a punt (similar to when a kick return team does not guard against the onside kick). That means there is a slight sample bias in the data due to pre-existing conditions.
All that said, the choice to fake or not to fake comes down to game theory. There should be an equilibrium when it comes to the success of 4th-down attempts and currently, there is not. As a result, it makes sense for teams to actually fake more often than they currently do until the success rates become equal. Again, keep in mind that the small sample sizes could mean that the difference is due to random variation, but it is definitely a starting point when it comes to strategic decision-making.