"The United States has the highest prison population rate in the world, some 738 per 100,000 of the national population, followed by Russia (611), St Kitts & Nevis (547), U.S. Virgin Is. (521), Turkmenistan (c.489), Belize (487), Cuba (c.487), Palau (478), British Virgin Is. (464), Bermuda (463), Bahamas (462), Cayman Is. (453), American Samoa (446), Belarus (426) and Dominica (419).
"However, more than three fifths of countries (61%) have rates below 150 per 100,000. (The rate in England and Wales - 148 per 100,000 of the national population - is above the mid-point in the World List.)"
Source: Walmsley, Roy, "World Prison Population List (Seventh Edition)" (London, England: International Centre for Prison Studies, 2007), p. 1.