The Willie Sutton Rule is based on a statement by notorious American bank robber Willie Sutton, who, when asked by a reporter about why he stole from banks, answered: “Because that's where the money is.”

In other words, his end goal was money so why waste time looking for it in obscure or questionable places instead of taking the path of least resistance and most success and going straight to the source? The rule can be applied across many different disciplines, from investing to medicine, science, business and accounting.