fair share

Etymology
First attested in the mid-1600s.

Noun

 * 1) An equitable or reasonable portion, especially in regards to contributions towards a particular duty, or the dividends thereof.
 * 2)  A significant amount, often implied to be excessive or inordinate; a great deal of something.
 * 1)  A significant amount, often implied to be excessive or inordinate; a great deal of something.

Usage notes

 * Prior to the 1950s, the indefinite "a fair share" was in equal usage as possessive forms, such as "their fair share". However, this has steadily declined, and according to Google Ngram data, possessive forms are now roughly four times as popular as the indefinite. The definite form, "the fair share", has never been common, and has fallen from a peak of 3.2% of total uses in 1989 to less than 0.7% in 2019.
 * To avoid ambiguity between the senses of "an equitable portion" and "an excessive amount", it is common to use the idiom "more than one's fair share".