The Diffusion of Artificial Intelligence in Corporate Disclosure: A Decade of S&P 500 10-K Filings, 2015–2025

This paper studies how artificial-intelligence (AI) disclosure in the Item 1A risk factors of S&P 500 10-K filings evolved between fiscal years 2015 and 2025. It asks three questions: when AI disclosure became common in Item 1A; whether firm characteristics explain which firms disclose and whether that power changes as disclosure spreads; and whether firms that write more AI text write less firm-specific AI language. The data are a panel of 5214 firm-years for the 501 firms in the S&P 500 as of April 2026, so the sample is subject to survivor bias; the coverage gap relative to the historical index is about 38% in 2015 and falls to 2% by 2025. AI mentions come from a hand-validated keyword dictionary, and a lexical distinctiveness score measures how far a firm’s AI wording departs from that of its peers in the same year; the score captures wording, not informational content or quality. Three results follow. First, the share of firms disclosing AI in Item 1A rises from 0.7% to 77.6%, with the largest jump in the first filing cycle after the November 2022 release of ChatGPT. Second, the power of firm characteristics to discriminate disclosers falls as disclosure saturates: the disclosure logit’s pseudo-R2 drops from 0.24 to 0.03 and the area under the ROC curve from 0.86 to 0.61. Third, among disclosing firm-years, more AI text is associated with lower lexical distinctiveness. These associations are descriptive; this paper does not test causal mechanisms.