Platform certification, seller disclosure, and fit uncertainty in online sports-goods supply chains

With the development of e-commerce, consumers purchasing sports goods online face not only quality information asymmetry but also common fit uncertainty due to differences in size, sports habits, and usage scenarios. To alleviate these issues, this paper constructs a three-tier game model using backward induction. Key findings: (1) Without certification, low-end manufacturers can offset brand disadvantages through stronger fit disclosure; high-end manufacturers do not always lead in quality or disclosure. (2) Platform certification creates market stratification, high-end manufacturers’ advantage grows with certification rigor, but only when they participate. (3) The platform’s optimal certification standard rises with consumer trust and commission rate, and falls with certification cost; platforms prefer standards that induce only high-end participation. (4) Certification’s effect on social welfare is non-monotonic, with a unique socially optimal level. (5) Excessive certification can crowd out manufacturer disclosure when the two are substitutes. The study reveals the synergistic and substitutive mechanisms of certification and disclosure, providing theoretical and managerial implications for platform certification design and manufacturer information strategies.