The number of people who died in the Paraguayan War (1864–1870) is unknown. Widely diverging estimates have been made. "Determining the size of Paraguay's population has always been an exercise in frustration."[1] However, there is a widespread impression that the casualties (military and civilian) were immense; there was also some population loss from non-lethal causes such as migration. The Dutch human geographer Jan Kleinpenning thought that Paraguay lost between a quarter and a half of its population, but much higher and lower estimates have been made. No academic demographic scholarship makes it less than 7% (including migration) or greater than 69%.