One area of controversy surrounding casinos is their relationship to crime rates. Economic studies that show a positive relationship between casinos and crime usually fail to consider the visiting population at risk when they calculate the crime rate in casino areas. Such studies thus count the crimes committed by visitors, but do not count visitors in the population measure, and this overstates the crime rates in casino areas. Part of the reason this methodology is used, despite it leading to an overstatement of crime rates is that reliable data on tourist count are often not available. In a 2004 report by the US Department of Justice, researchers interviewed people who had been arrested in Las Vegas and Des Moines and found that the percentage of problem or pathological gamblers among the arrestees was three to five times higher than in the general population. According to some police reports, incidences of reported crime often double and triple in communities within three years of a casino opening.