This problem is called lack of isochronism. For long this was recognized as a disturbing influence on the isochronism of the balance. This problem, called lack of isochronism, plagued mechanical watches throughout their history. The most common method of achieving isochronism is through the use of the Breguet overcoil. The superior performance of the deadbeat over the recoil is due to improved isochronism. The pendulum, due to its isochronism could be a much better timekeeper. This property, called isochronism, is the reason pendulums are so useful for timekeeping. Many keywind watch movements make use of a fusee, to improve isochronism.