80-20
Most widely, the 80-20 rule is an indication of inequality.
Whether that is of use
- of ethical fairness,
- or the practical division of work,
- or the effectiveness of perfectoinism,
- or of any other pattern you would like to point out.
It is named for the economist and general smart dude Vilfredo Pareto pointing out that 80% of Italy was owned by 20% of the population - an unequal distribution of wealth.