Stock index futures added to losses on Wednesday after the chief executive of Wal-Mart Stores Inc said he still sees stress in the economy and no quick end to the recession.

* S&P 500 futures fell 5 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 38 points, and Nasdaq 100 futures we're down 12.5 points.

(Reporting by Edward Krudy; Editing by Theodore d'Afflisio)