Cadwal Chronicles
The Cadwal Chronicles are a trilogy of science fiction novels by American writer Jack Vance set in his Gaean Reach fictional universe. The three novels are called Araminta Station (1987), Ecce and Old Earth (1991) and Throy (1992).
Background
Cadwal is a planet discovered by an explorer who is a member of the "Naturalist Society of Earth". The society decides to preserve Cadwal as a nature preserve and sets up a Conservancy based on a Charter. The Charter forbids mining and other exploitation, and permits strictly limited settlement. Only six "Agents", each in charge of a bureau with a staff of 20 men and 20 women, are allowed to reside permanently on the planet to enforce the Charter, although tourists are allowed in specially designed lodges, overlooking sites of natural beauty and interest.
From the earliest days, the Agents recruited relatives and close associates for their staffs, but as their numbers eventually exceeded the Charter limits, the excess remained on Cadwal as "collaterals" under the transparent fiction of being "temporary" labor. At their 16th birthday, each person learns their "index number", indicating their genealogical rank. A person whose index number is 20 or less upon their 21st birthday is granted Agency status; all others become lesser-status collaterals. Many collaterals choose to leave Cadwal to seek their fortune elsewhere in the Gaean Reach. Thus, the society of Cadwal is a highly stratified aristocracy, where success depends on birth as much as aptitude.