A trader works on the floor of the New York Stock Exchange.

A lot of strategists seem a bit nervous that more economic data will come in lower than expected. Thus far, their fears seem well-founded.

This morning saw a flurry of disappointing data: consumer confidence for September came in at 86, well below expectations of 92.6. Separately, September Chicago PMI, a measure of manufacturing activity in the Chicago area, also came in below expectations, at 60.5 (estimates of 61.9).