LONDON — Thousands of employees across 70 companies in Britain started the first day of a four-day workweek on Monday, a pilot program that is the latest test in the decades-long quest to scale back workers’ hours while they earn the same amount of pay.

The six-month trial was organized by the nonprofit groups 4 Day Week Global and 4 Day Week UK Campaign, and Autonomy, an organization that studies the impact of labor on well-being. Researchers at Cambridge University, Oxford University and Boston College will assess its effect on productivity and quality of life and will announce results in 2023, the organizers said in a statement.

The program in Britain follows similar efforts in other countries, including Iceland, New Zealand, Scotland and the United States, where companies have embraced greater flexibility in work hours as more people worked remotely and adjusted their schedules during the pandemic.

“After the pandemic, people want a work-life balance,” Joe Ryle, the campaign director for the 4 Day Week Campaign, said in an interview. “They want to be working less.”

More than 3,300 workers in banks, marketing, health care, financial services, retail, hospitality and other industries in Britain are taking part in the pilot, the organizers said. Mr. Ryle said the data would be collected through interviews and staff surveys, and through the measures each company uses to assess its productivity.

“We’ll be analyzing how employees respond to having an extra day