Market share

Market share is the portion of a market's total sales that one company captures, usually stated as a percentage. If a market brings in $100 billion a year and one company sells $28 billion of it, that company holds 28% of the market.

Share shows how a company is doing against its competitors, which revenue growth on its own can't. A company can grow quickly and still lose share if the whole market grows faster, and it can gain share while its sales shrink if competitors shrink more. Reading the two together shows whether growth comes from winning customers or from a rising tide.

A large and stable share often points to a durable advantage such as scale, brand or switching costs. A steady loss of share deserves attention even when results look strong, because it can mean competitors are catching up before it shows in the numbers.