Key findings from this report on the world's prison population include the following: as of May 2011, more than 10.1 million people were being held in penal institutions throughout the world, mostly as pre-trial detainees/remand prisoners or as sentenced prisoners; the countries with the largest prison populations were the United States (2.29 million), Russia (0.81 million) and China (1.65 million sentenced prisoners); the United States has the highest prison population rate in the world, 743 per 100,000 of the national population, followed by Rwanda (c. 595), Russia (568), Georgia (547), and the U.S. Virgin Islands. (539); as of mid-2010, the world prison population rate was 146 per 100,000, given a world population of 6.9 billion; prison population rates vary considerably between different regions of the world, and between different parts of the same continent; and prison population rates have been increasing in all five continents, with rates increasing in 78 percent of the countries and territories included in this report. Data for this report were obtained from a variety of sources: the national prison administration of the country concerned or else the ministry responsible for that particular country's prison administration. The primary purpose for this report is to show the differences in the levels of imprisonment across the world and to estimate the world prison population total. The data evaluated in this report cover the period from the end of 2008 through the beginning of May 2011. Tables