Vertical mobility is movement up and down a hierarchy of stratification. Those who gain in property, income or status are said to be upwardly mobile, while those who move in the opposite direction are said to be downwardly mobile. Intergenerational mobility compares the present social position of individuals with their parents. Intragenerational mobility compares the position of the same individual at different moments in the course of his or her working life. A further important distinction made in studies of social mobility is between structural and nonstructural mobility.
Structural mobility is movements made possible by changes in the occupational structure in society.
Nonstructural mobility is any movement which does not involve such changes. In sociology, the major focus of study has been on the character of intergenerational mobility within different societies. Different societies have different systems of stratification which will affect social mobility. The amount of vertical mobility in a society is a measure of its 'openness', this indicates the extent to which individuals will be able to move up and down the socioeconomic ladder. In principle at least, social mobility within a caste system of stratification is impossible as individuals are born into a caste.