In the late 1700s, when most Americans worked on farms or in small family business, the average full-time worker spent six days - a total of 72 hours a week, - on the job.
In the 1800s, as workers moved to jobs in large factories, employers shortened these hours by standardizing work to the tempo of the factory whistle and using new technologies to raise productivity.
The work week declined to 68 hours by 1860, and to about 65 hours at the turn of the century. By 1930, it was down to 50 hours a week.
The work week declined most dramatically - to 40 hours - in the Great Depression. This decrease was largely the result of the federal governments's attempts, as a matter of policy, to cope with mass unemployment by redistributing, or sharing, scarce work opportunities.
Since then, the average work week has held steady at 40 hours, though workers have gained additional time off in the form of annual vacations and holidays.
Now, the forces that have kept work time "propped up" since World War II are shifting, according to some observers, and "should tilt the scales" in the direction of increasing leisure, or time-off, once again.
These forces, which now seem to be abating, include the heavy family responsibilities of the post-war baby boom, the increasing costs of rearing and educating children, and the "persistent yearning for a rising standard of living" which followed the deprivation of the Depression and the war, according to labor economists Sar Levitan and Richard Belous.
Adding to the tilt toward leisure, they say, is a shift in the makeup of the labor force itself "in the direction of those (women and younger workers) who give added weight" to time off.
With reduced birth rates, and the growing number of multiple paycheck families, Levitan points out, "shorter hours don't necessarily mean a reduction of per capita income for a household."
Others point out that the old tyranny of the factory whistle is often no longer possible or even desirable, for employers as well as employees.
Indeed, according to economist John D. Owen, of Wayne State University, in general, the "worst possible work schedule" for making economic use of such costly public investments as trains, highway and parks "is a standard work week which forces nearly everyone into standard commuting and leisure time patterns.