The ranking was compiled by the Institute for Crime & Justice Policy Research (ICPR) at Birkbeck, University of London. It is based on data from the World Prison Brief 2025, an annual survey that measures prison population rates per 100,000 inhabitants and is updated once a year.

Under the methodology, the prison population includes people held in prisons and other penal institutions by decision of state authorities as a result of detention, remand, or a court sentence. Individuals serving administrative detention are not included in the calculations.

Compared with other CIS countries, Uzbekistan has one of the lowest prison population rates, ranking 166th. Turkmenistan has 576 inmates per 100,000 people, placing fourth worldwide. Russia records 300 prisoners per 100,000 people (35th place), Kazakhstan 163, and Tajikistan 145. Armenia is the only CIS country with a lower rate than Uzbekistan, at 83 inmates per 100,000 people.

El Salvador tops the global ranking with 1,659 prisoners per 100,000 inhabitants, followed by Cuba (794) and Rwanda (620).

The ranking covers UN member states as well as several territories with special status, for a total of 224 jurisdictions. Some countries, including Somalia, Eritrea, and North Korea, are not included in the ranking due to the lack of official prison population statistics.