Standard & Poor's announced several changes to the S&P MidCap 400 and SmallCap 600 Indices because of a spate of recent acquisitions.
Rackspace Hosting Inc. will replace AmeriCredit Corp. on the MidCap 400 after the close of trading Thursday, with AmeriCredit being taken over by General Motors Holdings LLC.
Watsco Inc. is replacing Hewitt Associates Inc. on the MidCap 400, while Super Micro Computer Inc. will take Watsco's place on the SmallCap 600. Hewitt Associates is being acquired by Aon Corp.
And Riverbed Technology Inc. will replace NBTY Inc., which is being take over by the Carlyle Group, on the MidCap 400.