In research that would be a welcome assignment to many an armchair quarterback, he reviewed almost 20,000 first quarter plays in 732 regular season games in 1998, 1999 and 2000 that were downloaded from the National Football League Web site. Armed with mathematical, statistical and economic tools, Romer zoomed in on fourth down decision-making and the rarely-questioned consensus that it's usually far better to kick than to go for a first down or touchdown.

Romer's working paper, "It's Fourth Down and What Does the Bellman Equation Say?" pulls off a dramatic turnover of this conventional wisdom.

"The results are striking," he said. "The analysis implies that teams should be quite aggressive...In practice, however, teams almost always kick on fourth down early in the game."

Teams would often fare better if they went for a first down or touchdown on fourth down, Romer said in his research, presented this summer to the National Bureau of Economic Research. The private, nonprofit, nonpartisan research organization is dedicated to promoting greater understanding of how the economy works.

In setting boundaries for his research, Romer decided to look at first-quarter plays to avoid the complications introduced when one team is well ahead of the other, or when the end of a half is approaching. And taking into account that decisions to go for a touchdown on fourth down are so rare, he analyzed the outcomes of third-down plays instead to determine what to expect if teams went for it on fourth down.

Romer started by considering the number of points involved - three for a field goal, seven for a touchdown - and the probabilities of the success of a field goal and the odds of making a first down or touchdown. The catch, Romer said, is to think ahead about what happens next, and what happens after that, and after that - a process summarized by a tool known to economists as the "Bellman equation."

To deal with this complication, Romer focused on 101 situations: a first down on each yard line, a kickoff from the 30-yard line, and a free kick from the 20-yard line following a safety. The Bellman equation and large data set allowed him to estimate an average value in terms of points for each of these situations.

When combined with information about the likely outcomes of kicking and going for it, these point values allowed Romer to determine which decision is better on average as a function of where the team is on the field and how many yards it needs for a first down or a touchdown. Then, he compared these results with the teams' actual choices.

On a team's own half of the field, going for it is better on average as long as there are less than about 4 yards to go for a first down, Romer found. After midfield, teams should generally be even more aggressive, he said.

Yet on the 1,100 fourth downs where Romer found it would be best to go for it, teams kicked 992 times.

Romer realizes that his conclusions run counter to conventional football wisdom. But he argues that the conclusions make sense if one thinks about them.

An example he gives in the paper concerns a team facing fourth and goal on the 2-yard line. The usual strategy is to attempt a field goal, which will almost certainly produce three points. In this situation, however, going for a touchdown has about a three-sevenths chance of success, and so, on average, produces about the same payoff in terms of immediate points. But because trying for a touchdown and failing leaves the opponent with the ball in terrible field position, thinking about what will happen next tips the balance in favor of the aggressive strategy.

Romer is curious why teams are so cautious, even when the rewards of a win, often nationally televised, are so high.

One possible reason may be that the costs of losing as a result of a failed gamble are much higher than the costs of losing due to playing it safe, he said. The coach opting for the play less taken may face jeering and complaining fans, critical sportswriters and sports talk show commentators, and costly reprimands from team owners.

Or maybe, Romer said, teams are really trying to win, but are just exhibiting human imperfection.

While it may seem Romer's work is out of bounds for an economist, it fits, in fact, into the burgeoning field of behavioral economics. So does the scholarship of many of his UC Berkeley colleagues, including Daniel McFadden and George Akerlof, winners of the Nobel Prize in Economic Sciences in 2000 and 2001, respectively.

The academic study of football offers several benefits, he said:

* The analysis demonstrates the ability of mathematical, statistical and economic tools to develop insights into a subject that, at first glance, seems to have nothing to do with those areas.

* Professional football team behavior offers a powerful test of economists' standard assumptions about risks, rewards and decision-making, their theory that people are "good maximizers."

* Football team behavior can help distinguish between competing explanations of failure.

* Football is fun: people like to watch it and talk about it.

Romer said his research was spurred by his own puzzlement, when listening to a football game on the radio, over why there were no questions about strategy on a fourth down.