The first significant economic indicators of 2008, to be released today following the close of the first market session of the new year, will be eyed carefully by investors trying to determine whether some of last year’s economic storms will blow over any time soon.

The Census Bureau will announce November’s construction spending figures, which could indicate whether the credit crunch — which began as a residential mortgage crisis — is beginning to damage the commercial real estate market. Also today, the Institute of Supply Management will publish its Purchasing Manager’s Index for the month of December, which could shed light on how well the manufacturing sector is weathering the current market turmoil.

“Over the last couple of years, as residential spending has declined, nonresidential has been very strong. However it now appears that nonresidential construction may be slowing,” the economic team at the finance and economic Web log Calculated Risk wrote of today’s construction spending numbers.

Nonresidential real estate cycles typically trail residential real estate cycles by about four to seven quarters, they wrote, which means America is due for a slowdown in commercial real estate.

A slowdown in commercial real estate activity may have already begun in Manhattan, where leasing activity year-to-date slowed in the third quarter by 12.3%, according to the brokerage firm Cushman & Wakefield.

“Because commercial real estate conditions lag economic conditions, the ongoing uncertainty in the financial markets has the potential to further curb the pace of leasing activity in the months to come,” Cushman & Wakefield analysts wrote in a recent industry report.

Not everyone is predicting a construction slowdown. Analysts at Reid Thunberg ICAP predict today’s report will show that the nonresidential building growth rate rebounded in November to about 0.8% more than October, even in the face of tighter financing.

“Unfortunately, we don’t think that will translate into any improvement for overall construction spending” because of weakness in residential spending, they wrote.

The consensus regarding the Institute of Supply Management’s Purchasing Manager’s Index for December is flat or down slightly. The index, which illustrates the health of America’s manufacturing sector, was 50.9 in November, down from 56 in June.

The ISM index “has fallen for five straight months, and while another drop in December can’t be ruled out, we think the index is likely to have been basically steady,” analysts at Reid Thunberg ICAP wrote.

A stabilized PMI index would indicate that the manufacturing sector, which is an essential building block of the American economy, is successfully weathering the current economic storm.