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