NEW YORK, Feb. 21, 2013 /PRNewswire/ -- S&P SmallCap 600 constituent Kilroy Realty Corp. (NYSE: KRC) will replace Jefferies Group, Inc. (NYSE: JEF) in the S&P MidCap 400, and Atlas Air Worldwide Holdings Inc. (NASD: AAWW) will replace Kilroy Realty in the S&P SmallCap 600 after the close of trading on Thursday, February 28. S&P 500 constituent Leucadia National Corp. (NYSE: LUK) is acquiring Jefferies Group in a deal expected to be completed on or around that date, pending final approvals.

Kilroy Realty is a real estate investment trust (REIT) that operates a portfolio of commercial properties. Headquartered in Los Angeles, CA, the company will be added to the S&P MidCap 400 GICS (Global Industry Classification Standard) Office REITs Sub-Industry index.

Atlas Air Worldwide Holdings provides outsourced aircraft and aviation operating services. Headquartered in Purchase, NY, the company will be added to the S&P SmallCap 600 GICS Air Freight & Logistics Sub-Industry index.

Following is a summary of the changes:

Additions to and deletions from S&P  Dow Jones Indices do not in any way reflect an opinion on the investment merits of the companies involved.

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