View Full Version : A New Study on Fourth Downs: Go for It

09-17-2009, 07:51 AM
A New Study on Fourth Downs: Go for It
By Brian Burke

(Brian Burke, a former Navy pilot who has taken up the less dangerous hobby of N.F.L. statistical analysis, runs Advanced NFL Stats, a blog about football, math and human behavior.)

Here’s a thought exercise for you. Imagine that for decades no one ever thought of the punt. Teams knew nothing else than to run or pass on 4th down. And then one day it’s invented. Some guy comes up to a coach and says, “Kick the ball on every 4th down and the other team gets possession 37 yards further down the field.” The coach would think he was crazy: “Wait, you want me to give up one quarter of my opportunities for a first down on every series…just for 35 yards of field position? Do you realize how much that’s going to kill our chances of scoring?”

And that coach would be absolutely right. It’s funny how boxed in our thinking can be. Except for the most desperate of circumstances or with inches to go just outside of field-goal range, today’s N.F.L. coaches will choose to punt.

Every single serious study of 4th-down decisions has found that, in most situations, teams would be better off by going for the conversion attempt rather than kicking. I’ve recently completed a study of 4th-down decisions that confirms what some fans already know, that it pays to be more aggressive. Those short on time might want to skip ahead to the bottom line.

In normal football situations, when neither team is ahead by much, and when the clock is not yet a factor, we can weigh the costs and benefits of each possible decision. Field-goal attempts, punts and conversion attempts can be valued by using a concept called Expected Points. A 1st down at any given yard line has an equivalent point value based on the average of the next score in the game. For example, a 1st down at midfield is worth 1.9 expected points.

Since we know the average punt distances and field-goal percentages from various field positions, we can accurately estimate the expected point values of kicks. And since we know the conversion percentages on 4th-down attempts, we can value those, too. When the values are compared, it becomes clear that going for the first down is the better decision far more often than most people, and most coaches, think.

You might ask: If it’s so obvious, then why don’t coaches go for it more often? There are a number of good explanations. The authors of the football research classic “The Hidden Game of Football” note that in the early days of the sport, it was rare for a team to score more than once all game. A punt basically guaranteed the opponent wouldn’t score on the next drive. Professor David Romer, author of one of the definitive papers on the subject, theorized that coaches are worried more about job security than winning. If a coach goes for it and fails, it’s his fault. But if he punts and loses, well, that’s just football, and his players take the blame.

I buy those explanations, but I also think it has something to do with what economists call Prospect Theory. In short, almost all people tend to fear losses far more than they value equivalent gains. In this perspective, a punt is considered the “break-even” decision. A failed conversion attempt is seen as a loss, and a successful attempt is seen as a gain. But the loss is feared disproportionately, and the result is clouded decision-making.

Above, I wrote “in normal football situations.” When time becomes a factor, or when a team falls far behind, we need a different way to analyze decisions. For these situations we need to rely on a Win Probability model, an index of how likely a team is to win based on all relevant game variables.

There’s an arbitrage opportunity in the N.F.L. right now. The first coach that takes advantage of a more aggressive 4th-down doctrine could win a whole lot of games, and N.F.L. strategy could get a whole lot more interesting.

09-17-2009, 11:15 AM
I may buy this to a certain degree for any number of teams with lessor defenses than ours...but between Sep and our D, I'd be comfortable punting on THIRD down in some situations!

09-17-2009, 01:29 PM
I don't really buy into this. I think these dudes have been playing too much Madden 2010!

09-17-2009, 03:38 PM
I don't really buy into this. I think these dudes have been playing too much Madden 2010!

4th and 37 pinned on your own 3 down 6 with 7 minutes to go in the game?

Go for it!

09-17-2009, 04:18 PM
Interesting article, but one thing it didn't touch on with regards to the human factor was the deflation of motivation of the team most effected: A failed 4th down boosts the opposing defense immensly and that effect is an intangible.