North Korea was founded in the late nineteen forties establishing a strict caste system as a way to maintain the survival of the new communist government. The newly established secret police and communist party reported on everyone making it possible to create an official list of every family assigned to one of 51 social classes. Most (29) of these classes were composed of people considered either hostile to the government or leaning that way. These new lower classes included business people, the most successful farmers, professionals, etc. Most of the population belongs to these 29 social classes. After decades of imprisonment or execution of any lower caste North Koreans who showed any sign of disloyalty, the survivors learned to hide their true feelings and forget nothing. This lower class lives bordering starvation, because of the permanent agricultural crisis. Incredibly, N.Korea's GNP is only about 30 billion dollars. The population has a high IQ but is undernourished and short.
The children of the higher-class families can afford more food and luxuries like electronic devices to view forbidden content stored on USB or MicroSD devices crammed with recent South Korean entertainment and news video. MicroSD cards are cheap (a few dollars for a Chinese or South Korean card that carries at least 32 gigabytes of data).