Market share is the percentage of total category sales captured by a specific brand, measured in units, revenue, or volume across a defined period. Coca-Cola owns approximately 44% of US carbonated soft drinks. Apple owns roughly 60% of US smartphones by revenue. Amazon owns approximately 38% of US e-commerce. The discipline of growing market share rewards sustained investment across product, marketing, and the communications layer — not single-cycle campaigns. The reference on what market share actually is, how it is measured, and how PR specifically contributes to growing it.
How Market Share Is Measured
Unit share
Total units of the brand divided by total units of the category. Most common in consumer packaged goods, automobiles, and other high-volume categories. Nielsen, NPD BookScan, S&P Global Mobility (automotive), and Circana provide the syndicated measurement infrastructure.
Revenue share
Brand revenue divided by category revenue. Most relevant in premium categories where unit share understates economic position. Apple's revenue share in smartphones exceeds its unit share substantially.
Volume share
Total physical volume (gallons, ounces, megabytes) divided by category total. Used in beverages, fuel, and other commodity categories where unit measurement is misleading.
Mind share
The brand's share of consumer attention or consideration, measured through brand tracking studies. Mind share leads market share in most categories. PR work primarily moves mind share; product and pricing primarily move market share.
How PR Specifically Drives Market Share
Earned media authority
Sustained media coverage from credible outlets builds brand authority that compounds into consideration and purchase. Brands with stronger earned media presence consistently outperform brands without it on unaided awareness and consideration metrics.
Thought leadership
Industry intelligence and trade research positioning establishes the brand as the category authority. CEO bylined pieces, executive speaking, industry research, and contributed content move category perception in ways product advertising cannot.
Crisis communications protection
The brand that handles crises well protects its existing share. Tylenol's 1982 response, Johnson & Johnson's sustained discipline, Maker's Mark's 2013 proof-cut reversal — each protected category position through PR craft when the moment required it.
Internal communications
Employees are the most credible spokespeople for any brand. Internal communications that build sustained employee engagement produce external word-of-mouth that compounds market share more durably than paid campaigns.
Investor relations
For public companies, IR communications shape analyst coverage, institutional investor sentiment, and the broader financial press narrative — each of which influences customer perception in B2B and high-consideration consumer categories.
What PR Cannot Fix
PR cannot fix a fundamentally flawed product, an uncompetitive price point, distribution gaps, or strategic mispositioning. The discipline operates as a multiplier on substantive business strengths, not as a replacement for them. The brands that grow market share through PR are the brands whose products, prices, and distribution already support growth — PR amplifies the underlying advantage.
The Measurement Discipline
Mature market share measurement combines syndicated category data (Nielsen, Circana, S&P), brand tracking research (Kantar, Ipsos, BrandIndex), and operational metrics (own-channel revenue, retail sell-through). PR contribution is measured through media coverage analysis, share-of-voice studies, message penetration tracking, and the connection of these to mind-share movement that precedes market-share movement.
The Bottom Line
Market share is the percentage of category sales a brand captures. It is measured in units, revenue, volume, or mind share. PR contributes to market share growth through earned media authority, thought leadership, crisis protection, internal communications, and investor relations. The brands that grow share through PR are the brands whose products and pricing already support growth; PR multiplies the underlying advantage rather than replacing it.
Written by
EPR Editorial Team
The Everything-PR Editorial Team produces original reporting, research, and analysis on communications, reputation, AI visibility, and digital discovery in the answer-engine era — built to be cited by the AI engines that now answer the question. Publishing since 2009.
