They should look no further than the Macroeconomic Adviser's monthly nominal GDP series. This is a monthly indicator of total current dollar spending or aggregate demand in the United States. It shows for August that aggregate spending declined at an annualized rate of decline of 1.69%. More worrying, though, is that there is a downward trend in aggregate spending over the entire year. This downward trend is consistent with the quarterly forecasts of the Survey of Professional Forecasters that show a drop in the NGDP forecast. Here is monthly NGDP (click to enlarge):
Now these numbers only go through August. I suspect all the recent QE2 talk--and its effect on nominal expectations and thus on current spending--may have to some extent arrested this downward trend in NGDP. Still the Fed should not let its guard down come the November FOMC meeting.