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Ahead of the Bell: Macerich to join S&P 500 index

NEW YORK (AP) -- S&P Dow Jones Indices LLC is moving real estate investment trust The Macerich Co. onto its noted S&P 500 index.

Macerich, based in Santa Monica, Calif., will replace Coventry Health Care Inc. on the index. Coventry is being removed due to its acquisition by Aetna Inc.

Aetna said Friday that it should wrap up its acquisition of the smaller health insurer Coventry within three business days.

Macerich was previously listed on the S&P MidCap 400 index.

Stocks added to the S&P 500 and other indices tend to see increased activity in the days surrounding the changes, because mutual funds and other investments that track the indices must purchase the stock to balance their portfolios.

Macerich shares closed Friday at $70.42, up nearly 21 percent since the start of the year. They added more than 2 percent in after-hours trading Friday following the announcement.

The move takes effect at the close of trading Wednesday and will trigger updates to several other indexes.

S&P SmallCap 600 constituent 3D Systems Corp., a printing company based in Rock Hill, S.C., will replace Macerich in the S&P MidCap 400. CoreSite Realty Corp., a real estate investment trust based in Denver, will replace 3D Systems in the S&P SmallCap 600.

McGraw Hill Financial Inc. owns the S&P index brand, along with other financial market indicators.