“Social Mobility is the movement of the individual or group upward or downward in the system of stratification”. Vertical mobility includes both upward mobility and downward mobility and it must be distinguished from Horizontal mobility in which an individual or group may change its occupation adopting another occupation with similar status.
Societies are distinguished on the basis of high or low vertical mobility into open societies and closed societies. In societies, therefore, there are few restrictions of birth on the ability to move into social positions but in close societies birth plays an important role in getting into social positions.
Openness or closeness is conceptual categories and no society is fully open or fully closed. Another distinction which must be made in the understanding of mobility depends upon the time for mobility.
Intra-generational mobility takes place in the same generation through a change in occupation. While inter-generational mobility marks a change in occupation from one generation to other that is from father’s occupation to son’s occupation.
“The institutions of mobility also differ so that mobility may be and often is understood in term of changes of occupation but it may also be in terms of level of education, prestige and power.