Prisoner population rate per 100,000 population by country. The map may be old. The latest data is here: Highest to Lowest - Prison Population Rate. From World Prison Brief. Incarceration rates are based on inmates in both prisons and jails. There is a more recent world map here: File:World map of prison population rates from World Prison Brief.svg
The map uses the following color legend:

  &gt;600
  400-600
  300-400
  200-300
  150-200
  100-150
  50-100
  &lt;50
  no data
File:World location map.svg
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