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.