The idea hit me in early 1977, during of all things a pistol match. And the ratio that first came to mind that weekend morning still seems about right. It is a rule — okay, a “guideline” as we now like to say — that explains and to a limited extent influences much of our daily lives. That morning I named it the 20 percent rule. In the — Lord help me — nearly 50 years since that day it has held up pretty well.