The election result has produced renewed interest in a 4-day week. The results of trials show that output was maintained at 5-day levels for most organisations that took part, resulting in many of them making the change permanent. A key point in these trials is that the reduced working hours do not result in reduced pay; this is a one-way bet for employees rather than some work-life balance trade-off they are making. Hardly surprising then that employees were keen to make a success of it.
The trials were over a short period and very recent, so what the results don't show is whether the benefits are permanent or, as I suspect, temporary.
The big hairy assumption underlying the trials is that there is some immovable curve, some fundamental natural link, between the length of the working week and employee productivity and that organisations are on the wrong part of this curve (5 days) and will achieve better overall productivity if they move to the right part (4 days). See the figure "Increased Prooductivity Offsets Reduced Hours" below.
But what if the true level of productivity is not set, or even heavily influenced, by the length of the working week? What if it is set by, say, how much of a dickhead your boss is? Or how useless your computer systems are? Or how stressful the daily commute is? Or how flawed your product? Or how many multiples of your salary the CEO takes home? Productivity in practice is a messy, unwritten compromise between employer and employee that settles out at a level where both parties are equally unhappy.
It is surely conceivable that the level of productivity is influenced by some range of factors like this which are not changed at all by shortening the working week, and that the equilibrium position remains pretty much where it was before, perhaps with some marginal improvement. In this case, the initial improvements are simply first-mover advantage and a sort of Hawthorne effect and the long-term picture might look rather more like the figure "Long-term Productivity Reverts to Former Level", below.
Now a couple of graphs don't make this science - they just illustrate my opinion. But companies that have already baked a 4-day week in to their employment terms based on these trials are - in my opinion - being brave. They might argue that they are taking other steps to lock in the productivity gains. Maybe they are addressing the computer systems and bad leadership as well. If so, why does that sensible management action have to be tied to a reduction in hours?
Beyond the impact on individual firms, a gradual move to a lower-output 4-day week becoming the norm across the UK would be bad news for GDP growth if, as I suspect, the long-term constant is the equilibrium level of productivity and not the shape of the curve (or, to put it another way, if the problem is how awful each working hour is for the employee and not how many of them there are in the week).
If you'd like to learn more about improving productivity in your business you should attend one of these events.
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