Protesters and law enforcement officers face off during a protest outside the Ferguson Police Department in October. Ferguson police statistics show the department arrest blacks at a higher rate than other racial groups — but that disparity is true for police departments across the country. Charles Rex Arbogast/AP hide caption

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Residents look on as Brazilian military police officers patrol Mare, one of the largest complexes of favelas in Rio de Janeiro, Brazil, on March 30. In one of the world's most violent countries, homicide rates are dropping — but only for whites. Mario Tama/Getty Images hide caption

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Outside New York City Hall, a policeman watches a protest against racial disparities in marijuana arrests. The majority of those arrested are black or Latino, even though those groups are not more likely to smoke pot. Andrew Burton/Getty Images hide caption

itoggle caption Andrew Burton/Getty Images