A similar model in France has been controversial for more than 15 years, ever since a Socialist government made a 35-hour workweek mandatory.

François Fillon, a conservative politician who is considered the front-runner to become France’s new president in elections this May, has vowed to kill it if he wins. Companies of all sizes in France have complained repeatedly that the short workweek requirement has damaged competitiveness and generated billions in additional costs. French unions defend the measure as protecting workers from employers who might otherwise return to more onerous workplace conditions.

Still, some large companies are beginning to explore the argument that happy workers may make better, more productive employees.

Amazon, Google and Deloitte recently began experiments to compress the 40-hour week into four days for some employees. Amazon, which has come under fire for encouraging employees to work long hours, announced last summer that it would test a 30-hour workweek for a small group of employees and managers, giving them 75 percent of their current pay but leaving them with the same benefits as other workers.

In the experiment at the Gothenburg retirement home, employees reported working with greater efficiency and energy when their hours were cut to six from eight a day. They called in sick 15 percent less than before and perceived their health to have improved at least 20 percent, according to a preliminary review issued last year.

At a nearby municipal retirement home, where a control trial left working conditions unchanged, employees reported increased blood pressure and said they perceived no improvement in their health, peace of mind or alertness, the review showed. A final report is scheduled to be released in March.

The program increased Gothenburg’s costs by 22 percent, mostly to pay for new employees. But around 10 percent was offset by reduced costs to the state from people being taken off the unemployment rolls and paying taxes into the system, rather than receiving state subsidies, Mr. Bernmar said.