The US listed options market is the largest in the world by premium and by the variety of what it lists. It is also the fastest-changing part of American trading. It began on 26 Apr 1973, when the Chicago Board Options Exchange opened in a smokers' lounge of the Chicago Board of Trade with standardised calls on a handful of stocks (16 classes on the first day, 911 contracts — OCC 50th-anniversary history), a month before Black and Scholes published their pricing formula. Fifty-two years later the Options Clearing Corporation (OCC), which stands behind every listed US equity and index option, cleared 15,207,163,554 options contracts in 2025, up 24.4% from 12,224,227,606 in 2024, inside a total of 15,263,912,452 cleared contracts (OCC release, 5 Jan 2026). OCC logged its 32 highest-volume days ever in 2025, two of them above 100m contracts, and a single-day record of ~110m on 10 Oct 2025, beating the >100m of 4 Apr 2025 (Cboe, "The State of the Options Industry: 2025"). The growth has a shape. Zero-days-to-expiry (0DTE) options, contracts bought and sold on the day they expire, were ~47% of S&P 500 index option (SPX) volume in 2024, a record 59% for full-year 2025 and a record 66.2% in July 2026 (Cboe monthly volume release, Aug 2026; always "share of SPX volume", not of all options). The market is spread across 16 to 18 exchanges owned by five groups (Cboe, Nasdaq, NYSE/ICE, MIAX, and BOX and MEMX; count verify), all of them trading the same multiply-listed equity options, while the most valuable index products (SPX, VIX) are proprietary to Cboe. Around them sit wholesalers that buy retail orders, market makers that hedge every trade, a single clearing house, and a tax code that treats an SPX option very differently from an option on the SPY exchange-traded fund that tracks the same index. This section explains how the market came to look like this, how its pieces fit, why 0DTE took over index options, what is known (and not) about who wins and loses, and how to choose between SPX, SPY and XSP. The companion worked example runs the same stylized trade through all three and shows what settlement style, assignment and Section 1256 tax do to the result.
What the study covers
- 1Overview: a standardised contract, many venues, one guarantor
- 2Units and definitions
- 3From put-and-call brokers to the Cboe and the OCC
- 4The exchanges: multiple listing and the fee war
- 5The products
- 6The rise of 0DTE
- 7Retail's share and single-stock short-dated options
- 8Volume records and what drives them
- 9Europe, India and Asia for comparison
- 10How to read options-market claims
- 11Key numbers
- 12Landmark firms and cases
- 13Pitfalls
- 14How an expert thinks about it
- 15Glossary
Technical exhibits
Worked examples, checklists and case studies included with this study.
Spx vs Spy Same Trade Worked Example
One stylized bull call spread held to expiry as 1 SPX, 10 SPY or 10 XSP contracts: contract counts and fees, cash vs physical settlement, early-assignment and pin risk on the SPY version, AM-settlement gap risk, and after-tax results under Section 1256 (60/40) vs short-term rates at three tax brackets (computed in Python, stylized)