Supported by religion and tradition, the estate system permitted quite a bit more mobility among social strata than did the caste system. Because only eldest sons could inherit the title and possessions of a noble family, the remaining sons had to enter either the military or the clergy. Occasionally, serfs who had distinguished themselves were freed and given land, and some peasants were allowed to enter the lower ranks of the priesthood. The remnants of the estate system are still visible in some modern societies that retain a landed gentry and inherited titles of nobility.

The Open Society: Class System

Modern industrial and postindustrial societies mostly nearly approximate the model of an open society. Open, or class, societies have a few common characteristics:

1. Classes exist but are not institutionalized as in the caste or estate systems;
2. Class lines are not very clear, so people do not display excessive class consciousness, but inequality stemming from class divisions is apparent;
3. Status is usually achieved, but there is evidence to indicate that status tends to be ascribed to the lowest and the highest social classes; and
4. Social mobility is possible and occurs frequently.

Open, or class, systems work best in industrial societies that have market economics, because these offer more opportunities for achieving wealth and status than do societies with centralized economies. In government-controlled economies, people may not have the opportunity to choose their jobs and maximize advantages.

Social mobility – essentially, changing class membership – is possible and encouraged in open systems; however, it is not evenly distributed in the society. Limitations based on racial, ethnic, regional, educational and even religious factors restrict mobility. However, the individual is still permitted much more leeway for social as well as physical movement than in closed systems.

As we have already discussed, class systems in all societies have certain characteristics in common. The rise of social classes is often accompanied by the development of central political institutions, foremost among which is the state. Further, the more surplus a society produces, the more stratified it is and the more complex its class system is. Even if in technologically advanced societies the large surplus that is produced filters down to almost all social classes and starvation-level poverty exists to only a very small extent, class inequalities remain flagrant. Finally, power and wealth appear to be the most important elements of class systems, with prestige playing a less important role.

In contemporary industrial societies, power and wealth are closely interconnected. In other words, the wealthy are more likely to come to power, and the powerful are likely to become wealthy. Societies that have a long tradition of feudal-like stratification, although they have become open in the industrial era, retain strong class boundaries.