What is advantages an disadvantages of oligarchy

pros: Oligarchies can be used for transformation, by insisting that monarchs or dictators share power, leading to power-sharing by other elements of society.

Decisions were made quickly.
Expert leadership and avoiding the rule of one.
Rulers were most educated.
Oligarchs worked together to rule effectively.

cons:Needs and wants of the common people are not thought of. Most leaders passed rules in favor of influential people.
Only privileged have say in who are elected their leaders
In many rules thousands of people are killed due to no freedom of speech or are 'enemies'
Things done quickly and efficiently as they do not need to be discussed with many
No one else to change the countries course if things are going wrong