The wikipedia definition is here: https://en.wikipedia.org/wiki/Market_share https://en.wikipedia.org/wiki/Market_share There are multiple methods of measurin

The wikipedia definition is here: https://en.wikipedia.org/wiki/Market_share https://en.wikipedia.org/wiki/Market_share There are multiple methods of measuring multiple (related) things. What you are describing sounds more like the share of the installed base, which only works for certain types of products. (i.e. it doesn't work for consumables like apples or electricity)