Whither the workweek?

Changes in hours worked normally track employment changes very closely. Recently, however, employment has increased more than hours, resulting in an unprecedented gap. In effect, the average annual hours worked have decreased by the equivalent of two weeks. Many factors can affect the hours worked. Some are structural or cyclical - population aging, industrial shifts, the business cycle, natural disasters, legislative changes or personal preferences. Others are a result of the survey methodology. How have the various factors contributed to the recent drop in hours of work?