1. North Korea: Lack of property rights
North Korea's economic institutions make it almost impossible for people to own property; the state owns everything, including nearly all land and capital. Agriculture is organized via collective farms. People work for the ruling Korean Workers' Party, not themselves, which destroys their incentive to succeed.
North Korea could be much wealthier. In 1998, a U.N. mission found that many of the country's tractors, trucks, and other farm machinery were simply unused or not maintained. Beginning in the 1980s, farmers were allowed to have their own small plots of land and sell what they grew. But even this hasn't created much incentive, given the country's endemic lack of property rights. In 2009, the government introduced a revalued currency and allowed people to convert only 100,000 to 150,000 won of the old currency into the new one (equivalent to about $35 to $40 at the black-market exchange rate). People who had worked and saved up stocks of the old currency found it to be worthless.
Not only has North Korea failed to grow economically -- while South Korea has grown rapidly -- but its people have literally failed to flourish. Trapped in this debilitating cycle, North Koreans are not only much poorer than South Koreans but also as much as 3 inches shorter on average than the neighbors from whom they have been cut off for the last six decades.