Open News has an interesting history of the camps that, among other interesting educated guesses, suggests that 50% of the largest camps’ (kwan-li-so) population is composed of people who are merely family members of those accused of disloyalty to the state:
The North Korean regime, as it consolidated its power, killed religious leaders, the pro-Japanese, and landowners, while imprisoning their family members in the so called “forced labor camps. In 1947, there were 17 of these forced labor camps. Between 1953 and 1956, Kim Il-Sung got rid of those who were against his regime, and there was a large-scale regulation and supervision of party members, and other civilians regarding their ideology. North Korea created a controlled district in order to isolate those who were brought in through regulation and supervision, this district contained several prison camps later on.
Between 1960s and 1970s, the North Korean regime consolidated the succession and dictatorship of Kim Jong-Il, and reinforced control and isolation over those against the regime. This process resulted in an expansion of prison camps.
The North Korean government also imprisoned family members of those who went to South Korea during the war. This happened during the education project for party members and categorization project of all citizens. The government also searched for Gapsan line, returned Korean-Japanese, Kim Dong-Gyu, who were decided to be a threat to the North Korean regime. #13 Jongsung Kwan-li-so had 5,000 prisoners in 1962, but in 1975, it held 20,000. For effective management, it was then divided into #12 Changpyung Kwan-li-so and #13 Jongsung Kwan-li-so. [Open News]
The camps are an essential part of the regime’s control over its subjects. In the past, the unspoken horror of being sent to a camp suppressed unhappy thoughts. Now that the regime is more-or-less openly hated, the horror of being sent to the camps mostly keeps that seething hatred in a passive state. Fear of the camps also has profound foreign policy implications for the United States, no matter how much the State Department may pretend otherwise. It is that fear that guarantees that North Koreans posted overseas will continue to obediently smuggle drugs, sell banned weapons, procure luxury goods, embezzle international development aid, defraud foreign insurers, violate U.N. resolutions, and launder the proceeds as ordered. It assures Kim Jong Il that North Korean scientists, technicians, and soldiers will never be forthcoming with American or U.N. inspectors or monitors who try to verify any disarmament agreement. It will continue to frustrate any attempt to distribute international food aid fairly.
New readers can see satellite imagery of the camps, in addition to a great deal of information culled from scholarly studies, at this page.