sentences:  The writing of the call option provides extra income for an investor who is willing to forgo some upside potential.The BXD Index is designed to show the hypothetical performance of a strategy in which an investor buys a portfolio of the 30 stocks in the DJIA, and also sells (or writes) covered call options on the DJIA Index.Investors have used exchange-listed options to engage in buy-write strategies since the 1970s, but prior to 2002 there was no major benchmark for buy-write strategies.