ladder vs social stratum

ladder

noun
  • A length of unravelled fabric in a knitted garment, especially in nylon stockings; a run. 

  • A frame, usually portable, of wood, metal, or rope, used for ascent and descent, consisting of two side pieces to which are fastened rungs (cross strips or rounds acting as steps). 

  • A series of stages by which one progresses to a better position. 

  • In the game of go, a sequence of moves following a zigzag pattern and ultimately leading to the capture of the attacked stones. 

  • The hierarchy or ranking system within an organization, such as the corporate ladder. 

verb
  • Of a knitted garment: to develop a ladder as a result of a broken thread. 

  • To ascend (a building, a wall, etc.) using a ladder. 

  • To arrange or form into a shape of a ladder. 

  • To close in on a target with successive salvos, increasing or decreasing the shot range as necessary. 

social stratum

How often have the words ladder and social stratum occurred in a corpus of books? (source: Google Ngram Viewer )