Changes in the job market, such as significant expansion or reduction within a particular career field, causing large numbers of people to move up or down the class ladder would characterize mobility.

social

Explanation:

Social mobility refers changes in an individual's social economic class within a stratification system. A social stratification system is the way society ranks individuals and families according to the social status. A person's or a family's social status is generally determined by wealth or power (or both).

When a person moves up the social ladder (stratification system) it means that they are improving their status and society generally perceives them as more valuable. E.g. Serguei Brin went from being a Russian immigrant to an extremely wealthy and powerful person after Google was a success. That is a clear example of a person moving up the social ladder.

People can also lower their social class when they lose their jobs and go through severe economic hardships.

d) social security number

let me know if i am correct or not, so i can edit the answer.

answer; measurable outcome;