What type of punch results in the most knockouts in boxing?

A boxing coach I met said that 70% of the knockouts in boxing come from the left hook since it has a small window of being telegraphed especially against a staggered opponent. My friend who boxed for 2 years and a lot of other online posters say that the straight right is the most common knockout punch since you can generate the most force from it. Any thoughts or evidence to support either?|||the straight right hand