Oxford's A Dictionary of Business defines this concept as the, "...share of the total sales of all brands or products competing in the same market that is captured by one particular brand or product, usually expressed as a percentage."

The Market Share Reporter, available via Gale Directory Library and Business Insights Essentials provides this type of data for many consumer products. Market share information can also be found in market research resources like Mintel Academic and Passport (Euromonitor) for market share for products in countries around the world.