The peak around the middle of 1960s was generated mostly because, based on the initial land-leasing contract, it became necessary in 1962 to make a yearly payment (from profits from the logging business) and therefore, it became necessary to log a huge amount of trees to make the payment.
1960年代中期のピークは、1962年に当初の借地契約による分収金の効力が発生し、その支払いに充当するために大規模伐採を進めていたことが大きい。