Key Takeaways
- Tracks 100 large-cap, blue-chip U.S. companies.
- Market-cap weighted; sector-balanced for stability.
- Basis for ETFs and options trading.
- OEX options are American-style, cash-settled derivatives.
What is OEX?
The OEX S&P 100 Index tracks the performance of 100 large-cap, blue-chip U.S. companies primarily listed on the NYSE and NASDAQ, offering a focused view of the biggest firms within the broader S&P 500. This index serves as a benchmark reflecting the health of major sectors and the overall economy, featuring companies like Apple and Microsoft.
Often associated with the Chicago Board Options Exchange, OEX also refers to options contracts based on this index, providing investors with tools for hedging and leveraged exposure.
Key Characteristics
The OEX index combines size, liquidity, and sector balance to represent the U.S. large-cap market efficiently.
- Market-Cap Weighted: Constituent weights correspond to float-adjusted market capitalization, emphasizing the largest firms.
- Sector Diversification: Designed to maintain balance across sectors, avoiding overconcentration.
- Blue-Chip Focus: Includes only stable, high-quality companies typically valued over $5 billion.
- Options Trading: The OEX options are American-style, allowing exercise anytime before expiration, unlike European-style indices.
- Index Calculation: Rebalanced quarterly to reflect changes in market capitalization and liquidity.
How It Works
The OEX index value is calculated by aggregating the market caps of its 100 constituents, adjusting for shares available to public investors. This weighting means that movements in companies like Apple or Microsoft can significantly influence the index level.
Investors access OEX exposure primarily through ETFs and derivatives rather than direct investment, using products tracked in guides like best ETFs. Options on OEX allow leveraged strategies and portfolio hedging, with a $100 multiplier and 5-point strike intervals providing precise risk management.
Examples and Use Cases
OEX serves as both a market benchmark and a foundation for investment products targeting large-cap U.S. equities.
- Technology Sector: Heavyweights such as Apple and Microsoft drive significant index movements, reflecting tech’s impact on the market.
- Portfolio Hedging: Investors use OEX options to protect blue-chip holdings from downturns without selling underlying shares.
- Large-Cap Investing: The index complements strategies found in resources like best large-cap stocks, focusing on stable growth companies.
Important Considerations
While OEX offers stability through its large-cap focus, it carries concentration risk because a few mega-cap firms can dominate index performance. This can lead to less diversification compared to broader indices.
Understanding related financial concepts, such as factor investing and call options, can enhance your ability to leverage OEX products effectively within your portfolio strategy.
Final Words
The OEX provides a focused view of the largest, most stable U.S. companies, making it a reliable benchmark for large-cap equity performance. Consider comparing OEX-based ETFs to diversify your portfolio with blue-chip exposure and assess their fees and liquidity before investing.
Frequently Asked Questions
The OEX S&P 100 Index tracks the performance of 100 large-cap, blue-chip U.S. companies primarily listed on the NYSE and NASDAQ. It represents a subset of the broader S&P 500, focusing on the largest and most liquid stocks across various sectors.
The OEX is weighted by market capitalization, meaning each company's influence on the index corresponds to its float-adjusted market cap. This weighting is periodically rebalanced to maintain sector balance and representation of the largest companies.
No, the OEX index itself is not directly investable. However, investors can gain exposure through ETFs, mutual funds, or derivatives that track the index, such as the iShares S&P 100 ETF (ticker: OEF).
OEX options are American-style, cash-settled derivatives traded on the Chicago Board Options Exchange. They provide leveraged exposure to the S&P 100 Index and can be exercised any business day before expiration, with settlement based on the index's closing value.
The OEX serves as a benchmark for the health of large-cap U.S. equities and the overall economy. It offers greater stability than broader indices by focusing on large, liquid companies, making it useful for fund managers and institutional investors.
Companies are chosen from the S&P 500 based on liquidity, size, and sector balance to ensure stability and broad representation. Selection is not solely based on market cap ranking but also considers maintaining sector diversity.
The OEX includes companies from various sectors such as technology, finance, healthcare, and more. Some well-known constituents are Apple, Microsoft, and JPMorgan Chase, reflecting a wide range of large-cap U.S. industries.


