All present is not correct Nowhere is it written in stone that ‘ye shall work five days a week’, so why are we so wedded to that?

‘Most people seem to think there is something inevitable or God-given about working five days’

The SNP is pondering the move, but there is a key debate to be had about the effects on labour and costs

Every so often someone proposes that the economy should move to a four-day working week, with the weekend extending across three days. Indeed, this idea is currently under active consideration by the SNP.

On the whole, when such suggestions are made they are widely condemned as the imaginings of crackpots. Although there is an awful lot of crackpottery around on this subject, in general the recent proponents of a shorter working week have been eminently sane. But there is a key debate to be had about the effects and the costs.

In the past, proponents of a shorter working week have often focused on the supposed shortage of jobs. They have argued that it would be fairer to spread the limited amount of work more equally over the population.

This idea is known by economists as “the lump of labour fallacy”.

As anyone who has the flimsiest knowledge of economic history will readily acknowledge, the number of jobs has risen dramatically over time roughly to match the number of people willing and able to do them. This is not accidental. It goes to the essence of how the economic system works. There are still some people who argue for a shorter working week on these grounds, often associated with the supposed disappearance of jobs because of robots and AI.

Yet, as I argued in my recent book The AI Economy, in this respect there is nothing different about this economic revolution from the economic revolutions that have gone before.

Yes, some jobs will disappear but others will spring up to take their place. Contrary to what you may have heard elsewhere, we are not about to experience “The Death of Work”.

The serious argument in favour of a shorter working week is that, as the economy becomes more productive and we as individuals become better off, we are able to afford to work less

– if we want to.

In essence, as the economy becomes more productive we face a stark choice. At one extreme, we could work just as much as before and take the whole benefit of our increased productivity in the form of higher incomes and consumption.

At the other extreme, we could decide against any increase in income and consumption and take the benefit of our increased productivity wholly in the form of reduced working hours and an associated increase in leisure time. And, of course, we could make any choice between these two extremes.

When I have suggested at conferences and other gatherings that we might be on the brink of moving towards a shorter working week, the general reaction has been one of incredulity. Most people seem to think that there is something inevitable or God-given about working for five days. Yet nothing could be further from the truth. If any length of working week is God-given then it is six days and not five, with the Sabbath acting as a day of rest, mirroring the day that God took off during Creation. And six days was indeed the normal working week until comparatively recently.

Moreover, if you look at history over long periods you see remarkable evidence on the variability of work patterns. Average working hours in the UK peaked at the time of the Industrial Revolution and have been trending down since.

Most striking of all is the data on average working hours going back to medieval times. In the late

14th century there was a sharp drop in the average number of hours worked across the year.

What could possibly explain this? The answer is the Black Death which afflicted Britain and other European countries in the middle of the 14th century. It dramatically reduced the workforce, perhaps by as much as a third. The result, unsurprisingly, was a sharp rise in real wages.

Medieval man reacted to this in a particular way. He seems to have had a target level of earnings in mind and when he reached that target level more easily because of higher real wages he decided to work less.

Accordingly, the average number of hours worked fell. So much for the idea of set working hours.

The idea of a shorter working week has recently received eloquent endorsement from a new book called Friday is the New Saturday by the economist Pedro Gomes.

One of the striking things about this book is that Gomes argues that working as hard as people currently do has such a deleterious effect on their productivity that when working hours are reduced, total output may not fall. In some sectors it could actually rise. If he is right about this, then there is no trade-off between working hours and incomes. We are faced with the prospect of having more leisure without losing any income.

I think Gomes is on to something for some parts of the economy – but not all. In major parts of the economy, fewer hours worked is going to mean less output. And that means lower real incomes.

But that doesn’t mean that a shorter working week isn’t going to happen. It would be more readily accepted if a fall in average working hours occurred gradually at a time of rising productivity.

In that case, an absolute drop in output and income could be avoided. They simply wouldn’t rise at the rate that they would have done if working hours had stayed the same.

Whether Gomes is right or not about the effect on productivity, if we are to work fewer hours then there are major social and economic questions about what we are going to do with the time thereby released.

At the very least, the leisure industries would have to expand still further and this would offer many opportunities for increased employment – albeit, presumably, not for five days a week.

The shape of our lives, including the shape of the normal week, would change dramatically. If Friday is the new Saturday then Thursday is the new Friday.