The 80/20 Rule (Pareto Principle)
The rough observation that ~80% of effects come from ~20% of causes — first noticed in income distribution and now applied to almost everything.
Origin
Italian economist Vilfredo Pareto observed around 1896 that 80% of Italian land was owned by 20% of the population, and that the same lopsided distribution appeared in many other countries and centuries. He found similar patterns in his own garden (80% of peas from 20% of pods). Joseph Juran, a 20th-century quality-management consultant, generalized it as the Pareto principle: 'the vital few and the trivial many.' Mathematically it is a particular kind of power-law distribution.
Modern usage
The single most-cited rule of thumb in business and self-help. '80% of your results come from 20% of your effort,' 'focus on the 20% that matters,' etc. Tim Ferriss's The 4-Hour Workweek (2007) is one long application of it. Frequently misapplied — the percentages are approximate, and not every distribution is Pareto.
In the wild
Cut the meeting list using Pareto — most of it isn't moving the number.— business common usage
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