TOKYO -- Seven-Eleven Japan is reassessing its mainstay 24-hour business model as franchise owners grapple with severe personnel shortages, testing shorter store hours at select locations to gauge the impact on earnings.

Starting in mid-March, 10 directly run stores will adopt the company's namesake operating hours of 7 a.m. to 11 p.m. in trials running at least a few months to see changes in sales and customer traffic. The convenience store operator under Seven & i Holdings will review the results to decide what to do with franchise locations, which account for 98% of all stores.

The convenience store leader has 20,000-plus Japanese locations. And 96% of them, excluding ones at such facilities as train stations and office buildings, are open around the clock.

The company has made 24-hour operation a basic rule for franchise locations not only for customers' convenience, but also because it has built its own production and logistics operations around this business model.

Franchise owners are hard-pressed to staff their stores, however. An Osaka Prefecture owner who cut daily hours to 19 in February has been accused by Seven-Eleven Japan of violating its contract. Franchise owners asked late that month for collective bargaining to negotiate shorter hours and other remedies.

The tight Japanese labor market has prompted many retailers and eatery operators to re-examine 24-hour operations. Lawson and FamilyMart Uny Holdings unit FamilyMart have also experimented with reduced hours at convenience stores. Royal Holdings ended 24-hour operation at Royal Host restaurants in 2017. McDonald's Japan, under McDonald's Holdings (Japan), halved 24-hour stores over three years through 2015 to around 800 locations.