Apple, the world's biggest technology company, has started monitoring weekly data on the working hours of more than one million employees in its production supply chain, which is largely located in China.
The iPhone and iPad maker quietly expanded this coverage last month from about 500,000 workers tracked in January, according to the company's updated "Supplier Responsibility Progress Report" published online.
"Ending … excessive overtime is a top priority for Apple in 2012," the report said.
Independent auditor the Fair Labor Association (FLA) said in August that Apple and its primary manufacturing contractor, Hon Hai Precision Industry, have made "steady progress" in trimming working hours and boosting safety measures at their three biggest mainland factories since more than 50 violations were uncovered by a comprehensive inspection in February.
Apple had revealed on January 13 its tightly guarded list of suppliers after announcing that it was admitted by the Washington-based FLA. Apple said the 156 companies in the list accounted for more than 97 per cent of its entire supply chain.
"Going deep into our supply chain, we now follow weekly supplier data for over 1 million workers," the updated Apple supplier report said. "In November, 88 per cent of workweeks were less than the 60-hour maximum specified in Apple's code of conduct."
The company added: "In limited peak periods, we allow work beyond the 60-hour limit for those employees that volunteer to do so."
The FLA said in August that Hon Hai, whose manufacturing subsidiaries are collectively known under the trade name of Foxconn Technology Group, cut working time to 60 hours a week, with the goal of meeting the 40-hour legal limit next July. The group also increased wages and enforced stricter working hours for interns.
Hon Hai, which employs about 1.2 million people across its electronics operations, had earlier been accused of labour-rights abuses which led to a series of worker suicides in 2010 and a fatal industrial accident last year.
The FLA's initial audit in February surveyed 35,000 workers at Foxconn's Apple-related operations in Guanlan and Longhua in Guangdong province and Chengdu in Sichuan province. It found that workers each averaged 56 hours per week, with maximum weekly working hours averaging 61 hours.
About 48 per cent of the employees surveyed thought that working hours were reasonable, 34 per cent would like to make more money and 18 per cent felt they worked too much.
In its updated supplier report, Apple said: "Our approach to reducing excessive working hours has evolved over the years from a small seed programme into a comprehensive approach that interlinks training, management consultation, integration with procurement decisions, and verification of work-hour practices and systems."
Apple also said its audits have been expanded to include 28 suppliers in Malaysia and Singapore.