NEW YORK (AP) â¿¿ Shares of staffing companies declined Tuesday in the wake of Friday's weak jobs report and continued worries about the European debt crisis. Monster Worldwide Inc., the parent company of jobs website Monster.com, was the biggest loser on the S&P 500. Monster shares lost 53 cents, or 6.1 percent, to $8.20 in afternoon trading. Stocks traded lower Tuesday on concerns that the European debt crisis is getting worse. On Friday, the Labor Department said U.S. employers stopped adding jobs in August and the unemployment rate remained at 9.1 percent. U.S. markets were closed Monday for the Labor Day holiday. In afternoon trading, shares of staffing company Manpower Inc. lost $1.52, or 4.1 percent, to $36. Shares of Kelly Services Inc. lost 56 cents, or 4 percent, to $13.40, while On Assignment Inc. stock slid 15 cents, or 2.2 percent, to $6.73. Robert Half International Inc. stock declined 39 cents, or 2.4 percent, to $15.85. Shares of TrueBlue Inc. slipped 33 cents, or 2.5 percent, to $12.81.