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Evidence · Digital & platforms

Social media, influencers and online word of mouth: the research

Online word of mouth is linked to higher sales on average, but the size of the effect varies with platform, product and whether review volume or ratings are measured. Brand posts on social media are associated with higher customer spending, and content that triggers high-arousal emotions is shared more. The effect of paid social advertising needs randomised experiments to measure, because observational methods often get it wrong. Research on influencers and B2B social selling is younger and relies mostly on reviews, interviews and surveys.

Definition

Social media marketing covers what firms and customers do on social platforms: electronic word of mouth (reviews, ratings, shares), content that spreads virally, posts published by the brand itself, paid social advertising, and paid or unpaid endorsement by influencers. In business markets it also includes social selling, where salespeople use social networks to find, understand and engage buyers.

What the research finds

Online word of mouth moves sales, unevenly

One meta-analysis of 1,532 effect sizes from 96 studies finds an average correlation of .091 between online word of mouth and sales, with volume mattering more than valence. Another, of 51 studies, estimates elasticities of .236 for volume and .417 for valence, higher for privately consumed, hard-to-try products and reviews on independent sites. A third pools 443 sales elasticities from 26 studies. The meta-analyses do not agree on whether volume or valence matters more.[1][2][3]

What gets shared, and what gets engagement

In about 7,000 newspaper articles plus experiments, content evoking high-arousal emotions (awe, anger, anxiety) or offering practical value was shared more, while sadness reduced sharing. Across 106,316 Facebook posts from 782 companies, humour and emotion raised likes, comments and shares; price and deal information lowered engagement on its own but raised it when combined with brand personality, and deals drove click-throughs.[4][5]

Brand posts convert, but fans skew heavy

Content published by a firm on social media was linked to higher customer spending, cross-buying and profitability beyond the effect of TV and email, most strongly for tech-savvy and socially engaged customers. For two packaged-goods brands, however, the Facebook fan base was concentrated among the heaviest buyers, the opposite of the brands' actual buyer base, so fans are a narrow audience.[6][7]

Paid social needs experiments

Comparing large randomised advertising experiments on Facebook with observational estimates of the same campaigns showed that observational methods often fail to recover the true effect. Power and sample-size calculations for platform lift tests are set out in a preprint that has not been peer reviewed.[8][9]

Influencers: credibility, fit and pacing

A review frames influencer marketing as borrowing the influencer's networks, positioning, content and follower trust. Four pre-registered studies find an inverted U for apparent age: very young or old influencers underperform, moderate ages engage most. Engagement also rises and then falls as creators post more often. An analysis of more than 100 person-brands identifies three ways they capture value: as advertisers, entrepreneurs or professionals.[10][11][12][13]

B2B social: mostly conceptual and survey evidence

Social selling has been defined from a literature review and practitioner study, then measured as insight generation, connecting and engagement, with management support driving adoption and thought leadership linking it to sales performance. A systematic review finds most B2B work treats social media as short-term tactics. Interview studies describe four B2B influencer strategies and content marketing practice, and experiments suggest sustainability messages that invite dialogue earn more engagement.[14][15][16][17][18][19]

How strong is the evidence?

The word-of-mouth evidence is broad, pooled across more than a hundred studies, but the meta-analyses show large variation and disagree on which review metric matters most. Much of the rest is observational and centred on Facebook; the fan-base finding covers two brands and comes from a research group known for its buyer-behaviour work. Influencer research is recent, and several key studies have barely been cited yet. B2B findings rest mainly on conceptual papers, interviews with small samples and surveys. The studies reviewed here say little about the economics of organic reach, paid formats beyond Facebook, or long-run brand effects of social activity.

References

  1. Ana Babić Rosario, Francesca Sotgiu, Kristine De Valck, Tammo H.A. Bijmolt (2015). The Effect of Electronic Word of Mouth on Sales: A Meta-Analytic Review of Platform, Product, and Metric Factors. Journal of Marketing Research.
  2. Ya You, Gautham Vadakkepatt, Amit Joshi (2015). A Meta-Analysis of Electronic Word-of-Mouth Elasticity. Journal of Marketing.
  3. Kristopher Floyd, Ryan Freling, Saad A. Alhoqail, Hyun Young Cho, Traci H. Freling (2014). How Online Product Reviews Affect Retail Sales: A Meta-analysis. Journal of Retailing.
  4. Jonah Berger, Katherine L. Milkman (2012). What Makes Online Content Viral?. Journal of Marketing Research.
  5. Dokyun Lee, Kartik Hosanagar, Harikesh S. Nair (2018). Advertising Content and Consumer Engagement on Social Media: Evidence from Facebook. Management Science.
  6. Ashish Kumar, Ram Bezawada, Rishika Rishika, Ramkumar Janakiraman, P. K. Kannan (2016). From Social to Sale: The Effects of Firm-Generated Content in Social Media on Customer Behavior. Journal of Marketing.
  7. Karen Nelson-Field, Erica Riebe, Byron Sharp (2012). What’s Not to “Like?”. Journal of Advertising Research.
  8. Brett R. Gordon, Florian Zettelmeyer, Neha Bhargava, Dan Chapsky (2019). A Comparison of Approaches to Advertising Measurement: Evidence from Big Field Experiments at Facebook. Marketing Science.
  9. C. H. Bryan Liu, Elaine M. Bettaney, Benjamin Paul Chamberlain (2018). Designing Experiments to Measure Incrementality on Facebook. arXiv.
  10. Fine F. Leung, Flora F. Gu, Robert W. Palmatier (2022). Online influencer marketing. Journal of the Academy of Marketing Science.
  11. Clara Galle, Vanessa Lau, Florian Dost (2026). Beyond youth: The optimal age for influencer credibility and marketing success. Journal of the Academy of Marketing Science.
  12. Wondwesen Tafesse, Mumin Dayan (2023). Content Creators' Participation in the Creator Economy: Examining the Effect of Creators' Content Sharing Frequency on User Engagement Behavior on Digital Platforms. Journal of Retailing and Consumer Services.
  13. Pierre-Yann Dolbec, Andrew N. Smith (2025). From fame and followers to fortune: How person-brands capture value in the creator economy. International Journal of Research in Marketing.
  14. Chiara Ancillai, Harri Terho, Silvio Cardinali, Federica Pascucci (2019). Advancing social media driven sales research: Establishing conceptual foundations for B-to-B social selling. Industrial Marketing Management.
  15. Harri Terho, Marta Giovannetti, Silvio Cardinali (2022). Measuring B2B social selling: Key activities, antecedents and performance outcomes. Industrial Marketing Management.
  16. Severina Cartwright, Hongfei Liu, Chris Raddats (2021). Strategic use of social media within business-to-business (B2B) marketing: A systematic literature review. Industrial Marketing Management.
  17. Joel Mero, Heini Vanninen, Joona Keränen (2022). B2B influencer marketing: Conceptualization and four managerial strategies. Industrial Marketing Management.
  18. Geraint Holliman, Jennifer Rowley (2014). Business to business digital content marketing: marketers’ perceptions of best practice. Journal of Research in Interactive Marketing.
  19. Sara Herrada-Lores, Ma Mercedes Cuyás Palazón Cuyás Palazón, María Ángeles Iniesta Bonillo, Antonia Estrella-Ramón (2024). The communication of sustainability on social media: the role of dialogical communication. Journal of Research in Interactive Marketing.

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Related topics

A synthesis of 19 studies, written by ScholarSignal. Last reviewed 2026-09-26.

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