계층이동이 · 계층이동을
social mobility, class mobility
Example
교육은 계층이동의 사다리라고 불립니다.
Education is called the ladder of social mobility.
Word parts
계 step+층 layer+이 move+동 move
Literally 'stratum moving'.
Good to know
Common phrase: 계층이동 사다리가 끊어졌다, 'the ladder of social mobility is broken'.