The Pareto principle, also known as the 80–20 rule, states that, for many events, roughly 80% of the effects come from 20% of the causes. The principle and named it after Italian economist Vilfredo Pareto, who observed in 1906 that 80% of the land in Italy was owned by 20% of the population; he developed the principle by observing that 20% of the pea pods in his garden contained 80% of the peas.
By applyng this principle to focus only on those tasks that contribute the majority of benefit in sinergy with the Parkinson's law (work expands so as to fill the time available for its completion) to limit the amount of actual time spent working, you'll be amazed by efficiency and effectiveness of work you'll be able to achieve.
More generally, the Pareto Principle is the observation (not law) that most things in life are not distributed evenly. It can mean all of the following things:
- 20% of the input creates 80% of the result
- 20% of the workers produce 80% of the result
- 20% of the customers create 80% of the revenue
- 20% of the bugs cause 80% of the crashes
- 20% of the features cause 80% of the usage
And on and on…
The key point is that most things in life (effort, reward, output) are not distributed evenly – some contribute more than others. The Pareto Principle helps you realize that the majority of results come from a minority of inputs. By knowing what theese inputs are you'll be albe to focus on them and achieve more. Remember that the Pareto Principle is an observation, not a law of nature. When you are seeking top quality, you need all 100%.