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CBOE S&P 500 BuyWrite Index (BXM)

SPX 1994.65 12.35
BXM 1068.07 0.78
BXY 1490.54 1.93
PUT 1437.25 0.00
CLL 657.48 0.00
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BXM Index Methodology (updated in November 2010, with an expanded VWAP period)
Historical Data Since June 30, 1986

The CBOE S&P 500 BuyWrite Index (BXMSM)

The CBOE S&P 500 BuyWrite Index (BXM) is a benchmark index designed to track the performance of a hypothetical buy-write strategy on the S&P 500 Index.

Announced in April 2002, the BXM Index was developed by the CBOE in cooperation with Standard & Poor's. To help in the development of the BXM Index, the CBOE commissioned Professor Robert Whaley to compile and analyze relevant data from the time period from June 1988 through December 2001. Data on daily BXM prices now is available from June 30, 1986, to the present time (see below). The BXM is a passive total return index based on (1) buying an S&P 500 stock index portfolio, and (2) "writing" (or selling) the near-term S&P 500 Index (SPXSM) "covered" call option, generally on the third Friday of each month. The SPX call written will have about one month remaining to expiration, with an exercise price just above the prevailing index level (i.e., slightly out of the money). The SPX call is held until expiration and cash settled, at which time a new one-month, near-the-money call is written. Please visit the BXM FAQ for more information about the construction of the index.

Experienced investors can ask their brokers about the possibility of engaging in an S&P 500 buy-write strategy by investing in stocks and SPX options.

Study on Index Options Writing by Asset Consulting Group

In February 2012 the Asset Consulting Group published a six-page paper -- "An Analysis of Index Option Writing for Liquid Enhanced Risk-Adjusted Returns". Key findings of the paper include:

  • Total Growth. Total growth for indexes since mid-1986 was 1153% for PUT Index, 830% for BXM Index, 807% for S&P 500 Index, and 368% for CLL Index (Exhibits 2 and 6).
  • Lower Volatility. The PUT, BXM, and CLL indices all had volatility that was about 30 percent lower than the volatility of the S&P 500 Index (Exhibit 4).
  • Left-tail Risk. Over the past 25 years, the worst monthly loss for the S&P 500 Index was a decline of 21.5 percent, compared to a relatively modest 8.6-percent monthly decline for the CLL Index (Exhibit 8e).
  • Risk-adjusted Returns. One measure of risk-adjusted returns, the Sortino Ratio, was 0.90 for the PUT Index, 0.75 for BXY, 0.71 for BXM, 0.50 for S&P 500, and 0.31 for CLL Index (Exhibits 10 and 11). Please note that all the indexes had negative skewness.
  • Monthly Premium Income. The average for the gross monthly premiums collected by the BXM Index was 1.8 percent. The index options usually were richly priced (Exhibits 12 and 13).

For more information, please see the six-page paper and press release.

BXM Study by Callan Associates

In 2006 Callan Associates, an investment services consulting firm, published a new study on the CBOE S&P 500 BuyWrite Index, with an analysis of performance from June 1988 through August 2006. Their study builds upon the earlier studies done by Professor Robert Whaley (now at Vanderbilt University) and by Ibbotson Associates. The new Callan Associates study had several key findings, including:

  • BXM generated superior risk-adjusted returns over the last 18 years, generating a return comparable to that of the S&P 500 with approximately two-thirds of the risk. (The compound annual return of the BXM was 11.77% compared to 11.67% for the S&P 500, and BXM returns were generated with a standard deviation of 9.29%, two-thirds of the 13.89% volatility of the S&P 500.)
  • The risk-adjusted performance, as measured by the monthly Stutzer Index over the 18-year period, was 0.20 for the BXM vs. 0.15 for the S&P 500. A comparison using the monthly Sharpe Ratio yielded similar results (0.22 vs. 0.16, respectively), confirming the relative efficiency of the BXM over the 219-month study period.
  • The BXM underperformed the S&P 500 during most rising equity markets and consistently outperformed the S&P 500 in all periods of declining equity markets, demonstrating the return cushion provided by income from writing the calls.
  • The BXM generates a return pattern different from that of the S&P 500, offering a source of potential diversification. The addition of the BXM to a diversified investor portfolio would have generated significant improvement in risk-adjusted performance over the past 18 years.

Click here for the study by Callan Associates.

Ibbotson Case Study on BXM Index

In September 2004 the Ibbotson Associates consulting firm issued a case study on the investment strategy represented by the CBOE S&P 500 BuyWrite Index (BXMSM). The study was three-fold: 1) assess risk-adjusted performance of the BXM; 2) evaluate the role of this covered-call strategy in a portfolio; and 3) establish if an investor can implement the strategy. Please visit these links to see a 4-page paper with a summary of highlights, a press release and the 35-page study.

Introduction to Buy-Write Strategies

A "Buy-Write" strategy generally is considered to be an investment strategy in which an investor buys a stock or a basket of stocks, and also writes covered call options that correspond to the stock or basket of stocks.

Buy-Write strategies provide option premium income that can help cushion downside moves in an equity portfolio, but Buy-Writes often under perform stocks in rising markets. Thus, some Buy-Write strategies significantly outperformed stocks in 2000 when stock prices fell, but Buy-Writes tended to under perform stocks in the years 1995 - 1998 when the S&P 500 rose by more than 20% per year.

Buy-Write strategies have an added attraction to some investors in that Buy-Writes can help lessen the overall volatility in many portfolios.

Historical Data Since June 30, 1986

The CBOE S&P 500 BuyWrite IndexSM (ticker symbol BXM) is a benchmark index designed to reflect the return on a portfolio that consists of a long position in the stocks in the S&P 500 index and a short position in an S&P 500 (SPX) call option. The historical return series for the BXM Index begins June 30, 1986.

BXM data for 2004 through the present (Updated Daily)
BXM data for June 30 1986—Dec. 2004

Spreadsheets with Historical Price Data

Historical Daily Prices - Spreadsheet with Closing Prices for Several Indexes
Historical Month-end Prices - Spreadsheet with Closing Prices for Several Indexes
In addition, Market Data Express gives users access to more than 16 years of historical options data

Links to More Information

Please click on any of the following for more information:

BXM Methodology (updated in November 2010)

BXM News Releases in:
April 2002
March 2003
June 2004
December 2004
September 8, 2006
September 28, 2006
May 23, 2007

"Most Innovative" Award
BuyWrite Indexes - Quick Reference Guide
S&P 500 (SPX) Index Options
Covered Call Strategy with Equity Options
Volatility Indexes
Volatility Concepts
BXM Monthly Roll Information, including VWAP and New Strike Prices
Sources of Returns for CBOE's BuyWrite Indexes

Index Charts

CBOE S&P 500 BuyWrite Index (BXMSM)

The CBOE S&P 500 BuyWrite Index (BXMSM) is designed to represent a proposed hypothetical buy-write strategy. Like many passive indexes, the BXM Index does not take into account significant factors such as transaction costs and taxes and, because of factors such as these, many or most investors should be expected to underperform passive indexes. Investors attempting to replicate the BXM Index should discuss with their brokers possible timing and liquidity issues. Transaction costs and taxes for a buy-write strategy such as the BXM could be significantly higher than transaction costs for a passive strategy of buying-and-holding stocks. Past performance does not guarantee future results. Standard & Poor's®, S&P®, and S&P 500® are registered trademarks of The McGraw-Hill Companies, Inc. and are licensed for use by the Chicago Board Options Exchange, Incorporated (CBOE). CBOE, not S&P, calculates and disseminates the BXM Index. The CBOE has a business relationship with Standard & Poor's on the BXM. LEAPS®, FLEX®, OEX®, XEO®, MNX®, CBOE® and Chicago Board Options Exchange® are registered trademarks of the CBOE, and SPXSM, and CBOE S&P 500 BuyWrite IndexSM BXMSM are servicemarks of the CBOE. The methodology of the CBOE S&P 500 BuyWrite Index is owned by CBOE and may be covered by one or more patents or pending patent applications.

Options involve risk and are not suitable for all investors. Prior to buying or selling an option, a person must receive a copy of Characteristics and Risks of Standardized Options (ODD). Supporting documentation for claims, comparisons, recommendations, statistics or other technical data is available by calling 1-888-OPTIONS, sending an e-mail to, or by visiting

Copies of the ODD are available from your broker, by calling 1-888-OPTIONS, or from The Options Clearing Corporation, One North Wacker Drive, Suite 500, Chicago, Illinois 60606. The information on this website is provided solely for general education and information purposes and therefore should not be considered complete, precise, or current. Many of the matters discussed are subject to detailed rules, regulations, and statutory provisions which should be referred to for additional detail and are subject to changes that may not be reflected in the website information. No statement within the website should be construed as a recommendation to buy or sell a security or to provide investment advice. The inclusion of non-CBOE advertisements on the website should not be construed as an endorsement or an indication of the value of any product, service, or website. The Terms and Conditions govern use of this website and use of this website will be deemed acceptance of those Terms and Conditions.

CBOE Volatility Index (VIX)