Synonyms: 80/20 rule, the Law of the Vital Few
Pareto Principle states that 80% of consequences come from 20% of causes. Speaking of UX, this principle goes like this: 80% of users use 20% of your features or 20% of the code causes 80% of the errors. In simple terms, this principle means that a small amount of effort has a significant impact.
Wilfredo Pareto, an Italian economist, noted that 80% of Italy's land belongs to 20% of the population. He then carried out surveys on a variety of the other countries and found that a similar distribution applied. Despite its origins, this principle can be applied to everyday life, economics, and design.