US murders concentrated in 5 percent of counties

Can anyone tell me what every one of theses counties have in common? The answer is at the bottom of the post. 

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US murders concentrated in 5 percent of counties

The majority of murders in the U.S. occur in only a small percentage of counties across the country. The Crime Prevention Research Center (CPRC) said in a new report that there is a “geographical concentration” of murders, with 68 percent of killings occurring in just 5 percent of the nation’s counties.

The answer:

  1. Areas with the highest gun ownership rates have low murder rates.
  2. All of them are Democratic controlled.