Shifting a company's entire operations into a new language isn't easy. But Neeley, who has studied corporate language strategy for a decade, has some suggestions.

• Companies need a clear, well-aligned strategy and "it needs to be supported and implemented at all levels of the organization, from the CEO down to the supervisor/manager of every employee who is subject to having to convert to a new language," she says.

• Off-the-rack tuition won't cut it. "English lessons alone are not enough," Neeley says. "If you have an aggressive environment where people work an extraordinary amount of hours and they're challenged with goals, language vendors need to help make sure you're capable of learning successfully while being successful at your job." The best results come when instruction is customized to employees' roles, with vocabulary geared specifically towards the types of emails they write, for instance.

• Go for broke. While some companies choose to become bilingual before adopting English wholesale, Neeley says this is "incredibly expensive and unsustainable."

• Those with English as a first language need to make adjustments too. "Native speakers need to learn how to dial themselves down and how to accommodate others," Neeley says.

• Managers should adopt a zero tolerance policy to backsliding, to make it clear that the change to English is not only possible but permanent.

Depending on the company's size, resources and the aggressiveness of its pursuit of English, Neeley estimates implementation is "a four to 10-year odyssey", with ongoing maintenance required thereafter. But she says the journey is worth it, pointing out that a company with English proficiency across the board has greater operational agility and "can serve all of their market seamlessly by using all of their human capital worldwide to achieve any end."

Immediately after acquiring a Canadian company, Rakuten was able to deploy seven of its top engineers to Toronto, to begin integration processes, according to Neeley.

"Two years ago they could have never done that," Neeely says. "That shows the extent to which expertise and knowledge flows through the company in ways it wouldn't otherwise."

For individuals too, there are benefits. Depending on their fluency and how far their career has advanced, an employee may experience performance anxiety and job insecurity when asked to work in a new language. But, Neeley says, as fluency increases, the emotional strain diminishes and bilingualism becomes something enjoyable. Perhaps even profitable.