on average vs ordinarily

on average

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

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

ordinarily

adv
  • In the usual manner; unexceptionally. 

  • Usually or as a general rule; commonly. 

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