market share 
noun
The portion of a market controlled by a particular company or product: a leading Internet service provider with a 15 per cent market share...
- It is the second largest producer of lime in Poland, with a market share of just under a third.
- However, the brand has steadied and increased its market share over the past two years.
- The new site certainly seems determined to live up to its English name by grabbing all the market share it can muster.