Americans spend more time on the job than workers anywhere else in the industrialized world, clocking nearly 2,000 hours per capita in 1997, up 4 percent from 1980, according to a new report by the International Labor Organization, a United Nations agency.

The United States has even surpassed Japan, long viewed as a nation of workaholics, with Americans now spending the equivalent of two additional 40-hour workweeks a year on the job compared with the Japanese, the report said. That's because the Japanese have reduced the number of hours they spent on the job per capita about 10 percent over the past decade and a half, dropping from 2,121 hours in 1980 to 1,889 in 1995, the latest number available for that country, while Americans increased their time on the job.

It's unclear why the two countries have shifted places in terms of workloads, and the report did not seek to interpret or explain the causes of this trend or others.

But the change may represent the normal ebb and flow of work when the economies are strong, with workers laboring longer when times are better and demand for products is high. It also may reflect the beginning of a shift in cultural values in Japan that is making long work hours less attractive.

The study's author, Lawrence Jeff Johnson, a labor-market analyst for the U.S. Bureau of Labor Statistics who worked with the ILO in preparing the report, said it is difficult to make generalizations based on the study because this is the first time these statistics had been collected and compiled.

Johnson said the ILO considers this effort a first step toward a more substantial analysis of how individual economies and their labor forces operate. It included data gathered from 230 countries.

In most of the rest of the Western world, most notably Europe, where workers already spent less time on the job, work hours continue to decline.

In Germany, for example, the number of hours worked dropped from 1,742 in 1980 to 1,560 in 1996; in Ireland, from 1,728 in 1980 to 1,656 in 1996; and in Spain, from 2,003 in 1980 to 1,809 in 1997.

In Australia, they dropped from 1,878 to 1,866; in Canada, they dropped from 1,785 in 1980 to 1,732 in 1996.

New Zealand and Sweden had slight increases.

In France, where legislation was recently introduced to limit the workweek to 35 hours, workers put in 1,656 hours in 1997, down from 1,809 in 1980.

One reason that workers spend less time on the job in European countries is that more vacation time is mandated by law. A recent college graduate in the United States, for example, typically will receive two, or possibly three, weeks of paid vacation in the first year of work, but European graduates automatically get four to six weeks.

The study reported, however, that workers put in longer hours in developing nations, such as Bangladesh, 2,301 hours; Malaysia, 2,244 hours; and Thailand, 2,228 hours, all in 1994, the most recent figures available.

Johnson said he hopes the report spawns additional study of which work patterns appear to be most productive economically and socially.

While some may view Americans' long work hours as essential to the country's continuing prosperity, Johnson said, others may question whether the nation is reaching a point of diminishing returns, when workers begin to become less productive because of burnout.

"How do the hours of work affect the quality of life?" Johnson asked. "Is this something we need to look at? . . . What is the impact on us collectively as individuals and on the family level?"

On productivity, which is the amount of goods and services produced for each hour worked, American workers rated highest, the ILO said. But the report indicated many other nations, particularly Ireland, Japan and most of the Western European countries, are making striking productivity gains.

"The productivity race is like a never-ending marathon in which the U.S. worker today is ahead of the pack, but a significant number of competitors . . . are picking up speed with the U.S. in their sights," Johnson said, noting that these countries are making the gains despite working fewer hours.