100/0 rule - you should be 100% certain 0% of the time. 80/20 rule - 80% of output is caused by 20% of effort (not literally true, but true in spirit most of the time). 77/23 rule - the poorest 77% of the world’s population accounts for approximately 23% of the world’s income (GDP figures 2010) [1] 75/25 rule - not more than 25 percent of the total unlicensed seaman on board a documented vessel shall be aliens lawfully admitted to the United States for permanent residence [2] 70/30 ...