A MODEL FOR COAL PRODUCTION BY PRISONERS IN NORTH KOREA

The objective of this study has been to develop a model for estimating coal production by prisoners in North Korea based on eyewitness accounts, satellite imagery, and historical data on non-mechanized coal mining. The first steps have been addressing the following questions: (1) Can production rates reported by eyewitnesses be trusted? (2) Are all reported prisoner coal mines currently in production? According to analyses of eyewitness accounts, a typical prisoner coal mining team works three eight-hour shifts per day and produces 3 metric tons per worker per day and 10 metric tons per coal picker per day. For non-mechanized coal mines in the USSR in 1935, the norm for a coal picker was 7.3 metric tons for a six-hour shift, closely corresponding to the North Korean coal picker productivity on an hourly basis. However, the reported North Korean per worker productivities are historically unprecedented for non-mechanized coal mining. The historical maximum non-mechanized productivity was that of Pennsylvania (US) anthracite mines, being 2.52 ± 0.13 and 2.06 ± 0.15 metric tons per worker per day for underground (1915-1935) and total production (1900-1935), respectively. The productivity of US bituminous coal mines was 2.33 metric tons per worker per day prior to the invention of coal-cutting machinery in 1892. More relevant might be the productivity of 0.69 metric tons per worker per day in the USSR in 1927-28. It is most likely that the calculated per worker productivity in North Korean prisoner mines has not taken into account all workers, such as managerial and support personnel, security guards, and children. The time series of satellite images was used to show that all underground anthracite mines at a reported prisoner mining complex were in active production as of the most recent image (April 3, 2019). The evidence for active production includes expansion of the surface footprints of coal waste mounds, the construction of terraces on waste mounds, the deposition of additional lobes on existing waste mounds, and the displacement of waste mounds and construction of mining infrastructure in the vacated space. The recent deposition of coal waste is also evident from the lack of Pinus densiflora (Korean red pine), which grows readily on coal waste and which can be seen on the older coal waste mounds.