constrain vs scale back

constrain

verb
  • To reduce a result in response to limited resources. 

  • To force physically, by strong persuasion or pressuring; to compel; to oblige. 

  • To keep within close bounds; to confine. 

scale back

verb
  • To make a reduction in the amount, extent, etc. of something. 

How often have the words constrain and scale back occurred in a corpus of books? (source: Google Ngram Viewer )