The answer is Market share
For example is the search engine product in US' Market.
In US , 60 % of internet users use google , 30 % of internet users use bing ( after it combined with yahoo), and the other 10 % use other search engine( such as Baidu,Naver, Geocities, etc).
From data above, we could conclude that Google has 60 % of market share in search engine product, Bing has 30 % marketshare, etc
