The peak of the business cycle has been declared as December 2007. From the nicely exposited statement by the NBER Business Cycle Dating Committee:
The Business Cycle Dating Committee of the National Bureau of Economic Research met by conference call on Friday, November 28. The committee maintains a chronology of the beginning and ending dates (months and quarters) of U.S. recessions. The committee determined that a peak in economic activity occurred in the U.S. economy in December 2007. The peak marks the end of the expansion that began in November 2001 and the beginning of a recession. The expansion lasted 73 months; the previous expansion of the 1990s lasted 120 months.
In the explanation that followed this introductory paragraph, the payroll employment series -- and its steady decline since December 2007 -- played an important role in determining the peak.
Read the whole thing.