NEW YORK, April 15 /PRNewswire/ -- S&P 500 constituent National OilwellVarco Inc. (NYSE: NOV) will replace S&P 500 constituent Rockwell AutomationInc. (NYSE: ROK) in the S&P 100, and Affiliated Managers Group Inc.(NYSE: AMG) will replace Grant Prideco Inc. (NYSE: GRP) in the S&P MidCap 400after the close of trading on Monday, April 21. Grant Prideco is beingacquired by National Oilwell Varco in a transaction expected to close on orabout that date pending final approvals. Rockwell Automation will remain inthe S&P 500.

Standard & Poor's will monitor these transactions, and post any relevantupdates on its website: www.standardandpoors.com.

National Oilwell Varco, headquartered in Houston, TX, engages in thedesign, construction, manufacture, and sale of systems, components, andproducts to the oil and gas industry worldwide.

Affiliated Managers Group provides investment management services tomutual funds, institutional clients, and high net worth individuals.Headquartered in Prides Crossing, MA, the company will be added to the S&PMidCap 400 GICS (Global Industry Classification Standard) Asset Management &Custody Banks Sub-Industry index.

    Following is a summary of the changes:
                       S&P 100 INDEX -  April 21, 2008
                                     GICS ECONOMIC                      COMPANY           SECTOR        GICS SUB-INDUSTRY
    ADDED     National Oilwell Varco    Energy      Oil & Gas Equipment                                                     & Services    DELETED   Rockwell Automation     Industrials   Electrical Components                                                     & Equipment
                    S&P MIDCAP 400 INDEX -  April 21, 2008
                                    GICS ECONOMIC                      COMPANY          SECTOR        GICS SUB-INDUSTRY
    ADDED     Affiliated Managers     Financials    Asset Management &               Group                                 Custody Banks    DELETED   Grant Prideco             Energy      Oil & Gas Equipment                                                     & Services

Additions to and deletions from an S&P equity index do not in any wayreflect an opinion on the investment merits of the companies concerned.

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