generally vs on average

generally

adv
  • As a rule; usually. 

  • Without reference to specific details. 

  • Popularly or widely. 

  • In the general case, without exception. 

on average

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

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

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