FRANCES O’GRADY, the head of Britain’s Trades Union Congress, threw down a gauntlet on September 10th. “We can win a four-day working week,” she told members. While partly a reflection of the emboldened state of Britain’s unions, the demand is far from unprecedented. Shorter working weeks have been tried in New Zealand and Sweden, where they resulted in happier, healthier and more motivated employees. Those who work shorter weeks are also reported to be more productive. Should weekends, therefore, be lengthened?

A five-day working week has been the Western norm for less than a century. The Reformation cemented Sunday as a holy day in Europe, but the day was often used for less-than-sober activities. With factory hands sometimes reluctant to work hard on all other days, 19th-century bosses started granting a half-day holiday on Saturdays to encourage workers to apply themselves during the week. The widespread adoption of the five-day, 40-hour working week took several more decades though. Industrialists such as Henry Ford pioneered it in the early 20th century and, nudged by unions, governments capitulated. In France the Matignon Agreements of 1936 put the 40-hour week into law, and America mandated two full days of freedom in 1940. Not every country was so quick: China’s Communist Party only allowed workers to shift to five working days in 1995. Last year full-time workers in the OECD, a group of rich countries, laboured for 40.1 hours per week on average.

France’s experience suggests workers may not leap at the chance of toiling for fewer hours. The government reduced the full-time worker’s week to 35 hours in 2000. The move was derided as little more than symbolic at the time, and so it has largely proved. Last year the French worked 38.9 hours a week on average (admittedly among the lowest figures in the OECD), seeming happy to labour above the required threshold and pocket the extra pay or holiday allowance. The rise of the gig economy has also reduced calls for fewer hours. For many workers the feasibility of a three-day weekend depends on whether they can afford to skip a shift. And businesses may not seize the opportunity either. In February a German metalworkers’ union won its members the right to work for the equivalent of four days a week, but the concession was described as a burden by the employers’ federation. It did not want to pay employees the same amount as before for working fewer hours. Working less may be linked to higher productivity (on a per-hour basis), but overall output could still fall because of the smaller number of hours worked. That will not get governments or employers excited.

Advocates of a four-day week could claim that improving people’s quality of life is more important than boosting the economy. In an essay published during the Great Depression, John Maynard Keynes predicted that workers in the rich world would one day be faced with the problem of how to spend their free time. He wrote of an “age of leisure and abundance” in which technological advances would allow people to work 15-hour weeks. Unfortunately for any readers toiling on a Friday afternoon, Keynes jumped the gun. Even Ms O’Grady, now angling for a longer weekend, is tellingly pessimistic in her timescale. A four-day week is apparently achievable “in this century”.