oligarchy
noun
GOVERNMENT, ECONOMICS uk/ˈɒlɪɡɑːki/ usplural oligarchies [ U ]
the fact of a country being ruled or controlled by a small group of powerful people:
The real difference between oligarchy and democracy is wealth.
[ C ]
a country or industry that is controlled by a small group of powerful people, or these people considered as a group:
The electricity industry has moved from being a state monopoly to being a de facto oligarchy.