Quote from : Scorecasting: The Hidden Influences Behind Sports and How Games Are Won Book

Inside the opponent’s 45-yard line, facing anything less than fourth and eight, teams are better off going for it than punting. Inside the opponent’s 33-yard line, they are better off going for it on anything less than fourth and 11.* Regardless of field position, on anything less than fourth and five, teams are always better off going for it.