The 3-6-3 rule is a slang name for unofficial banking practice that emerged in the 1950s, 1960s, and 1970s as a result of the industry’s non-competitive and simple circumstances. The 3-6-3 rule outlines how bankers are expected to pay their depositors 3% interest on their accounts, then lend them money at 6% interest and be playing golf by 3 p.m. A large portion of a bank’s business in the 1950s, 1960s, and 1970s was lending money at a greater interest rate than what it was paying out to its depositors (as a result of tighter regulations during this time period).