The 80-20 rule, also known as the Pareto principle, is a principle that states that roughly 80% of the effects come from 20% of the causes. This rule is named after Vilfredo Pareto, an Italian economist who observed this pattern in the distribution of wealth and income in society.

The principle is widely applicable and can be seen in various areas of life, business, and economics. Here are some common examples:

1. Business: In many businesses, it is often observed that approximately 80% of the company’s revenue comes from just 20% of its customers. Similarly, 80% of the company’s profits may come from a smaller fraction of its products or services.

2. Time management: The 80-20 rule is often used to prioritize tasks and focus on the most important activities. It suggests that 80% of the results can be achieved by concentrating on the top 20% of tasks that yield the most significant impact.

3. Sales: In sales, salespeople may find that 80% of their sales come from 20% of their clients.

4. Productivity: The rule can also be applied to personal productivity, where 80% of the output can be attributed to 20% of the effort or time invested.

5. Quality control: In manufacturing and quality control processes, the majority of defects or issues often come from a small number of causes.

It’s important to note that the 80-20 rule is a general guideline, and the percentages may not always be precisely 80% and 20%. It can be 70-30, 90-10, or some other distribution. The main idea is to recognize that a disproportionate impact is often created by a small subset of factors, and by identifying and focusing on these high-impact factors, one can optimize efficiency and results.