Definition of "gerontocracy"

It would come as no surprise to find that optimum science policy is apt to be developed neither by gerontocracy nor by juvenocracy but, like the community of scientists itself, by age-diversified meritocracy.

1972, Harriet Zuckerman, Robert K. Merton, “Age, Aging, and Age Structure in Science”, in Matilda White Riley, Marilyn Johnson, Anne Foner, Aging and Society, volume 3 (A Sociology of Age Stratification), New York, N.Y.: Russell Sage Foundation, page 337

But in his 1996 novel, Holy Fire, [Bruce] Sterling imagines a rather different future: a world ruled by an all-powerful gerontocracy, which appropriates most of the world's wealth to pay for ever more costly life-extension techniques.

1997 March 9, Paul Krugman, “Does Getting Old Cost Society Too Much?”, in The New York Times‎

He [Koizumi] was what would pass for a political maverick among Japan's faceless gray gerontocracy.

2018, Mikiso Hane, Modern Japan: A Historical Survey‎, 5th edition, Routledge