How large should the strike zone be in "three strikes and you're out" sentencing laws?

So-called "three strikes and you're out" sentencing laws for criminal offen ders have proliferated in the United States. The laws vary considerably in their definitions of what constitutes a "strike." This paper adapts the cla ssic Poisson process model of criminal offending to investigate how varying sentence lengths and definitions of what constitutes a strike affect the e ffectiveness and cost-effectiveness of these sentencing laws. In particular , it asks whether, by using different definitions for the first, second, an d third strikes or different sentence lengths, one can make the resulting i ncarceration more "efficient" in the sense of incapacitating more crimes pe r cell-year served.