Why Run When You Can Pass?

Life is getting tough for the running backs of the NFL. First comes the news that becoming a star rusher doesn't require a Heisman Trophy or even a high-profile start in NCAA Division I-A:

The debate has simmered for a decade, at least since the Denver Broncos began making a habit of turning unsung players into 1,000-yard rushers. Other championship-caliber teams, like the Indianapolis Colts and the New England Patriots, began casting aside top running backs, finding younger and cheaper alternatives with no regrets.

But the question of whether N.F.L. running backs are overvalued -- generally not worth the attention and money paid to them -- has intensified in recent weeks, as a number of unheralded and little-known players have taken leading roles with their teams.

Running backs may be the most interchangeable parts of a football team. Mel Kiper Jr., the N.F.L. draft expert for ESPN, said he would never choose one in the first round.

"I've been saying this for 30 years," Kiper said. "The easiest position to find a player is running back."

The steadily diminishing value of running backs has paralleled the ascent of the passing game. Since 1960, quarterbacks have managed to increase their average gain per pass attempt by nearly 30 percent, from 4.6 yards to 6.5 yards. (Running backs only get about 4 yards per attempt.) Furthermore, even as quarterbacks have gotten more yards per pass, they have managed to throw fewer interceptions. In 1980, passes were picked off more than 6 percent of the time. By 1995, the rate of interceptions had been halved, which meant that passing the ball wasn't any statistically riskier than rushing. For more on this subject, check out Michael Lewis' fantastic book, The Blind Side.

Which brings me to my last point: even though NFL teams are passing more than ever, they still aren't passing enough. That, at least, is the conclusion of Ben Alamar, a professor of sports management at Menlo College. He argues that the NFL exhibits a "Passing Premium Puzzle". (This is the sports version of the Equity Premium Puzzle, which is the mystery of why investors hold so many low yield bonds when stocks perform so much better over the long-term.) Alamar notes that, despite the significant increase in the expected utility of the passing game, coaches still run the ball about 46 percent of the time. While this represents a decrease from the 1960's - the average NFL team use to run the ball more than 58 percent of the time - a perfectly rational coach would almost always choose to pass, since passing represents a higher rate of return. So why do coaches still run the ball? Alamar admits that a successful running game contributes to the success of the passing game. But he isn't convinced that coaches need to run the ball quite so often. "For all of their planning and late nights," Alamar writes, "NFL coaches do not act in a fully rational manner." Just like investors choosing bonds over stocks, coaches are swayed by the illusory perception of risk. Although passing the ball isn't statistically riskier than running the ball, it seems riskier, and so coaches opt for the safety of the rush. It feels safer, even though it isn't.