NYSE Arca has proposed amending current listing rules in equity index-linked, commodity index-linked and linked currency securities (Index-Linked Securities) to eliminate a requirement prohibiting the number of components underlying an Equity Index-Linked Security from increasing or decreasing by more than 33 1/3 from the original number of index components at the time of listing. NYSE Arca states that investors in Equity Index-Linked Securities purchase these securities on the belief that the underlying index methodology is accurately described and maintained in order for the index to continue to represent the sector, geographic region or other investment characteristics the index is designed to track. With terms running up to thirty years in duration, it is likely that some of these indexes will change in ways that will bring them out of compliance with the “33 1/3 Requirement.”

NYSE Arca has also proposed changing its rules to list Index-Linked Securities that provide for payment at maturity based on a multiple of the direct or inverse performance of an underlying reference asset, with any negative payment at maturity limited to a multiple of twice the underlying reference asset. This listing standard for Index-Linked Securities will make them more analogous to exchange-traded funds like the Short Funds and UltraShort ProShares Trust and the Inverse Funds and Leveraged Inverse Funds of the Rydex ETF Trust, each of which trade on NYSE Arca pursuant to unlisted trading privileges.

 http://a257.g.akamaitech.net/7/257/2422/01jan20071800/edocket.access.gpo.gov/2007/pdf/E7-24033.pdf

 http://a257.g.akamaitech.net/7/257/2422/01jan20071800/edocket.access.gpo.gov/2007/pdf/E7-23971.pdf