on average vs substantially

on average

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

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

substantially

adv
  • Without material qualifications. 

  • In a strong substantial manner; considerably. 

  • To a great extent; in essence; essentially. 

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