[jpatokal]

The mortality rate in the Kolyma gulags was estimated at 27%/year, meaning the odds of survival for 15 years were <1%, and virtually zero for general work (mining etc). Shalamov survived because he managed to land a position as a hospital attendant.

[resc1440]

This assumes that random people die each year. However, if you survive for a year, you are probably very tough, and your life expectancy might actually go up.