SEOUL, South Korea (AP) — For more than a half-century, a mysterious caste system has shadowed the life of every North Korean. It can decide whether they will live in the gated compounds of the minuscule elite, or in mountain villages where farmers hack at rocky soil with handmade tools. It can help determine what hospital will take them if they fall sick, whether they go to college and, very often, whom they will marry.

It is called songbun. And officially, it does not exist at all.