Blatantly ripped from wikipedia:
http://en.wikipedia.org/wiki/Logan's_Run
Logan's Run is a novel by William F. Nolan and George Clayton Johnson. Published in 1967, it depicts a dystopian future society in which population and the consumption of resources is managed and maintained in equilibrium by the simple expediency of killing everyone upon reaching a particular age, thus neatly (and, according to the story's moral, "inhumanely") avoiding the issue of overpopulation which was of growing concern at the time. The story follows the actions of Logan, a Deep Sleep Operative or "Sandman", as he "runs" from society's lethal demand.