What part of the body contributes the most to generating the maximum speed of the golf club head?

This single answer allowed me to make a huge leap in my understanding of the golf swing, and in everything I had seen and read about the golf swing none of it emphasised it enough.

I carried out a survey on the Internet over several weeks and asked visitors to my web site the question:- What part of the body contributes the most to generating the maximum speed of the club head?

Only 20% got the answer correct