14 Data obtained through Polymarket’s Gamma API (https://gamma-api.polymarket.com/events/keyset). A list of names and tickers of the S&P 500 constituents as of May 11, 2026 was obtained from FactSet Research Systems, Inc. on May 12, 2026. Common words in the event contracts, such as “on”, “app”, “mar”, “tech”, “hd”, “ice”, “ball”, “low”, “now”, and “all” were excluded from the matching process. Categories that are not relevant to the matching, including sports, crypto, esports, weather, politics, geopolitics, Grammys, and Oscars, were also excluded. Common words that happen to be company names and/or tickers are more frequently used with a different meaning in the titles of select categories. For example, “mar”, Marriott International, Inc.’s ticker, often means the month of March in the politics category (e.g., “Donald Trump # of Truth Social posts Mar 21-28?”); “ball”, Ball Corporation’s ticker, is frequently used as a name of an award in the sports categories (e.g., “Will Lionel Messi win the Golden Ball at the 2025 FIFA Club World Cup?”); and “on”, ON Semiconductor Corporation’s ticker, is often used as a preposition (e.g., “Ethereum above $3,300 on August 2?”). To avoid overcounting mentions of companies, such common words and categories were excluded from the matching process.
15 See CFTC Advisory on Enforcement Authority over Event Contracts, Release No. 9185-26 (Feb. 25, 2026) available at https://www.cftc.gov/media/13351/Enf_AdvisoryKalshi022526/download; CFTC, CFTC Charges U.S. Service Member with Insider Trading in Nicolás Maduro-Related Event Contracts, Release No. 9217-26 (Apr. 23, 2026), https://www.cftc.gov/PressRoom/PressReleases/9217-26.
16 See Wall Street’s Top Cop Expects Enforcement on Prediction Markets, Bloomberg, February 5, 2026, https://www.bloomberg.com/news/articles/2026-02-05/wall-street-s-top-cop-expects-enforcement-on-prediction-markets.
17 Justin Wolfers and Eric Zitzewitz, “Prediction Markets,” Journal of Economic Perspectives 18, no. 2 (2004): 107–126; Joyce E. Berg, Forrest D. Nelson, and Thomas A. Rietz, “Prediction Market Accuracy in the Long Run,” International Journal of Forecasting 24, no. 2 (2008): 285–300.
18 Anthony M. Diercks, Jared Dean Katz, and Jonathan H. Wright, Kalshi and the Rise of Macro Markets, NBER Working Paper No. 34702 (National Bureau of Economic Research, 2026).
