Nisbett and Cohen's archival studies in the United States found that none of these statements are correct. Prior to the Civil War, there were more slaves in the hills and dry plains than in the moist plains. The homicide rate within the rural U.S. South is larger in the moist plains than in the hills and dry plains. All kinds of homicide rates are higher in the U.S. South than in the North. The difference in argument-related homicide rates between the U.S. South and North is more pronounced between large cities in the South and North than it is between rural areas within the South and North.