on average vs thereabouts

on average

prep
  • Expressed as a measure of central tendency (usually the arithmetic mean). 

  • Usually, typically; as a rule; as often as not. 

thereabouts

adv
  • About or around that date or time. 

  • Approximately that number or quantity. 

  • About or near that place. 

  • About or near to that condition or quality. 

noun
  • Location; whereabouts. 

How often have the words on average and thereabouts occurred in a corpus of books? (source: Google Ngram Viewer )