In the 1930s, economist John Maynard Keynes predicted that modern technology would give workers more leisure time. In fact, it seems it has just given bosses new ways to interrupt their employees’ holidays or evening trips to the pub.

On 8 April, French employees tried to claw some of their leisure hours back, after unions and employers’ federations representing nearly one million workers signed a legally binding deal stipulating that workers should not have to check their work emails after they leave the office, and that they should turn off their work mobiles. Already under French law workers are limited to a 35-hour week, unless they sign a contract agreeing to opt out.

In Sweden too, there are experiments to reduce the working week. The city of Gothenburg has proposed a year-long trial in which half of its municipal workers will work traditional eight-hour days while the remainder will work six. The government of Gothenburg has a hunch that this could increase productivity: in the 1930s the breakfast cereal maker Kellogg’s replaced its factory workers standard eight-hour-shifts with six hour ones and saw productivity increase.

There's no hard and fast link between working hours and productivity. It’s easier to see how six-hour shifts might boost the productivity of manual labourers or factory workers, who might physically tire, but what about office jobs? It often feels as though work expands to fill the space allocated to it – but a lot also depends on office culture. In some work places employees feel a great pressure to sit at their desks long after office hours end – even if all they’re doing is surreptitiously checking Facebook – because running out of the office at 5.01 “looks bad”.

In certain professions, such as corporate law and investment banking, unsociable hours and all-nighters are seen as a badge of honour. The UK is quite bad for this, 12 per cent of workers work more than 50-hour weeks, compared to an OECD average of 9 per cent (although we lag behind Turkey, where almost half of workers put in more than 50 hours a week.)

The OECD also publishes figures (summarised here) on the average hours worked in European countries and worker productivity. Generally, it does seem that reducing the number of hours worked increases productivity: Greeks for instance, work the longest average hours in Europe, putting in an average of 2,032 hours a year, but they are the 8th least productive workers. After Greece, Poland and Hungary work the second and third longest average hours respectively, but Poland’s workforce is the least productive in the OECD, followed by Hungary. The five countries that work the fewest hours (Netherlands, Germany, Norway, France and Denmark respectively) are all in the top ten most productive OECD countries.

The UK, meanwhile ranks 14th both in terms of hours worked and productivity. In the past five years since the start of the recession UK productivity has fallen, and according to the Office for National Statistics output per hour worked is now 21 per cent lower than the G7 average. Would it help if standard working hours were cut?

France’s inflexible labour laws are in many other ways a headache for employers, but campaigners for shorter working weeks are probably on to something. So go on, clock off early today. Not only is it perfect pub weather in London, but in the long term your boss might thank you for it.