In-group bias has been observed when it comes to traffic citations, as black and white cops are more likely to cite out-groups. A 2013 report by the American Civil Liberties Union found that blacks were "3.73 times more likely than whites to be arrested for marijuana possession," even though "blacks and whites use drugs, including marijuana, at similar rates." A 2020 study in the journal "Nature" found that black drivers were stopped more often than white drivers, and that the threshold by which police decided to search black and Hispanic drivers was lower than that for whites (judging by the rate at which contraband was found in searches). Analysis of more than 20 million traffic stops in North Carolina showed that blacks were more than twice as likely as whites to be pulled over by police for traffic stops, and that blacks were more likely to be searched following the stop. There were no significant difference in the likelihood that Hispanics would be pulled over, but Hispanics were much more likely to be searched following a traffic stop than whites. When the study controlled for searches in high-crime areas, it still found that police disproportionately targeted black individuals. These racial disparities were particularly pronounced for young men. The study found that whites who were searched were more likely to carry contraband than blacks and Hispanics. In-group bias by voters has also been suggested as possibly causing disparities, as voters discount criminal acts done by their in-group and thus will vote for higher enforcement in areas where the minority population is higher due to the lack of in-group leniency, allowing for racial disparities in the justice system even if the authorities are unbiased.