"Murder rates are highest in cities with populations greater than 250,000 and decline for each decreasing city-size category, to a low of 3.0 per 100,000 for cities under 10,000. A similar pattern is seen for robbery, where arrest rates are over six times higher in the largest, as opposed to the smallest, cities. However, there are no clear differences in arrest rates across city size categories for the crime of larceny-theft. Although rural-urban distinctions based exclusively on size of place are not ideal, this pattern of a strong relationship between city size and violent crime rates and weaker relationships for property crimes generally holds for several different societies and in several different historical periods."

http://law.jrank.org/pages/1990/Rural-Crime-Urban-rural-crime-differences.html