ACS Affiliated Computer Services, Inc.

Standard & Poor's said Friday it will add retailer Urban Outfitters Inc. (URBN) to its S&P 500 index to replace business-services provider Affiliated Computer Services Inc. (ACS), which is set to be acquired by Xerox Corp. (XRX).

Urban Outfitters will be added to the S&P 500 Apparel Retail Sub-Industry index.

As a result of Urban's move, Intrepid Potash Inc. (IPI) will be added to the S&P MidCap 400 Fertilizers & Agricultural Chemicals Sub-Industry index.

The date of the changes weren't announced.

Urban's shares were up 3.5% at $32.67 in after-hours trading, while Intrepid's were up 4.9% at $25.70. The shares of companies joining the S&P 500 often rise because many portfolio managers try to track the index and must buy shares of the companies that become part of it.

-By John Kell, Dow Jones Newswires; 212-416-2480; john.kell@dowjones.com