For centuries societies have been divided in stratums, organized by wealth and power. Before democracies arrived, societies used to be divided by royalties, nobles and clergy at the top level; followed by artisans and merchants; vassals; and slaves at the bottom level.
When democracies recently appear in many parts of the Western World, societies were divided in wealthy at the top, a new medium class, and the poor at the bottom. Politicians and clergy were mixed in different stratums.
With the recent dramatic development in technology, and with the appearance of new and more capable system for energy storage, a new stratum will appear in societies right between the medium class and the poor: The Robots.
Robots will directly compete with human in many jobs and services, and those (groups of) humans not capable of performing better than a Robot (physical works, and / or in intellectual and emotional capabilities) will have to be deleted gradually from the societies (through compulsory birth control programs).