Stock index futures added to losses on Thursday after data showed applications for unemployment insurance rose unexpectedly in the latest week.

S&P 500 futures fell 5.4 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 dropped 43 points and Nasdaq 100 futures lost 9.75 points.

Futures fell earlier as moderate Chinese manufacturing data fueled worries about the strength of global economic growth.

(Editing by Jeffrey Benkoe)