A United States researcher says that more than 400 markets are operating across North Korea with the approval of North Korean authorities.
 
Curtis Melvin, a researcher at the U.S.-Korea Institute at Johns Hopkins University's School of Advanced International Studies, told the Voice of America that satellite images identified 406 markets across the communist country. It marks a twofold increase from 2010.
 
Melvin said that markets, which became a critical means of living for North Koreans, remain in existence regardless of the size or government policies.