In a way, four-day working is already with us. Many people do not work what is currently regarded as the full, or standard, working week of five days, Monday to Friday.
It is the form of the four-day week that is the cause of debate. Should it be the standard? Should there be a commensurate reduction in pay? Which four days are to be worked? Can the four days be worked flexibly?
There is no clear right or wrong in legal terms. It is a matter of what employers and employees can settle upon. It may be that employees work a condensed week, keeping the same overall hours but only working four days out of five. It could also be that the equivalent of four full days are worked over a period of five weekdays.
We are so accustomed to the idea of five weekdays and two days at the weekend that it will take a long time for any new structure to be formulated and put in place, if at all. If flexibility is the aim, there may be no need to change our current base. Flexibility against a common reference point is already achievable.
In the end, it comes down to money. Will an employee be any worse off? The answer to this second question could easily be yes. Where employers seek to offer reduced hours rather than give a pay rise, we are in effect looking at a move away from full-time to part-time, based on the current standard.
There is well researched evidence about the health benefits of working fewer hours. The pay-off is that the work that is carried out could be done more efficiently in a reduced amount of time. The output therefore can, in certain circumstances, remain the same.
However, for many employers, where there is no immediately measurable output, there will be an increase in costs if salaries remain the same. A security guard, for instance, does not become more efficient with their role by working fewer hours. If their working week was to be cut by one-fifth with no commensurate decrease in salary, the cost base increases by 20%.
Any migration to the four-day week will inevitably be uneven depending on the work circumstances and by necessity, the financial wellbeing of an organisation. This means there will be perceptions from sector to sector, and possibly in the same organisation.
While there may be an initial clamour for change, there will be a considerable number of both employers and employees who are reluctant to change because the sums do not add up.
Martin Williams is head of employment and partner at Mayo Wynne Baxter