80/20 Rule for Designers

The 80/20 rule asserts that approximately 80 percent of the effects generated by any large system are caused by 20 percent of the variables in that system.

80 % of a product's usage involves 20% of its features.

80% of progress comes from 20% of the effort.

80% of errors are caused by 20% of the components.

80% of innovation comes from 20% of the people.

Great explanation by Randa Clay: 80/20 rule