Economy of North Korea
Estimating gross national product in North Korea is a difficult task because of a dearth of economic data and the problem of choosing an appropriate rate of exchange for the North Korean won, the nonconvertible North Korean currency. The South Korean government's estimate placed North Korea's GNP in 1991 at US$22.9 billion, or US$1,038 per capita. In contrast, South Korea posted US$237.9 billion of GNP and a per capita income of US$5,569 in 1991. North Korea's GNP in 1991 showed a 5.2% decline from 1989, and preliminary indications were that the decline would continue. South Korea's GNP, by contrast, expanded by 9.3% and 8.4%, respectively, in 1990 and 1991.
Korean currency
The history of Korean currency dates back around 3rd century BC, when first coins in the form of knife coins, also known as "Myeongdojun" belonging to the state of Yan and Gojoseon said to have been circulated. Grain coins were put to use within the kingdoms for a long period of time. The kingdom of Goryeo issued its own version of grain coins and till 1097. The first iron and bronze coins minted in Korea occurred during the 15th year (996 AD) of the reign of King Seonjeong. During the reign of King Sukjong, a monetary system of casting a variety of coins was established in the years 1097-1107. These coins included the 東國 (Dongguk "Eastern Country"), 海東 (Haedong "Eastern Sea") and 三韓 (Samhan "Three States") series of coins. Coins made from metals other than iron like copper and also silver vase-shaped coins (unbyŏng 銀瓶) were issued in the 10th and 11th century but their circulation was limited).