The "Gulag Archipelago" reference got me googling:
http://seansrussiablog.org/2013/05/11/us-prison-industrial-c....
Apparently, if you compare apples to apples, in 1953 the USSR period had more like 7.4 million "adults on probation, in jail or prison, and on parole". 2.61% of total population vs 0.76% in present US.