American CEOs have raised doubts about the effectiveness of having their employees work from home during the COVID-19 pandemic, with several, including the head of one of the biggest US banks, saying that it reduces productivity.

Jamie Dimon, CEO of JPMorgan Chase, said that he doesn't believe that working from home is beneficial. He said that he found that productivity dipped among young bankers on Mondays and Fridays and ordered his trading floor staff back to the office this month.

Dimon told a virtual conference in September: "I don't know the future better than anyone else. I think going back to work is a good thing. I think there are negatives to working from home. … We've seen productivity drop in certain jobs and alienation go up in certain things. So, we want to get back to work in a safe way."

His outlook appears to reflect others in the banking world, where less than half of the 250 banks and brokerages polled by FIS, a US-based international provider of financial services technology and outsourcing services, said they would let their workforce continue to work from home for the foreseeable future.

In New York, the giants of the banking world used to have tens of thousands of workers in high-rise office buildings who now are working remotely.

Manhattan has one of the largest business districts in the country. Collectively, JPMorgan Chase and Morgan Stanley lease more than 10 million square feet of office space in New York for their 20,000 employees.

The change to the workforce has had a huge impact on rent for commercial real estate in major international cities like New York and London because workers vacated buildings six months ago.

In New York, retail rent has dropped below $700 per square foot for the first time since 2011, CNBC reported. In central London, office rent will fall by 8 percent this year due to lower demand, according to asset managers DWS Group.

Before the pandemic, just 14 percent of American employees worked from home, according to the US Bureau of Labor Statistics. But since March, 42 percent of the US labor force now works from home full time, according to data from Stanford University.

Reed Hastings, the co-CEO of Netflix, is not a fan of working from home. He told The Wall Street Journal: "I don't see any positive elements. Not being able to meet in person, especially at the international level, is a downside."

Yet, some bosses now believe that the reaction to COVID-19 has changed the need for offices for good.

"The supply and demand for office space may change significantly," said Warren Buffett, chairman and CEO of Berkshire Hathaway, at the company's annual meeting in May. "A lot of people have learned that they can work at home, or that there's other methods of conducting their business than they might have thought from what they were doing a couple of years ago. When change happens in the world, you adjust to it."

"Is it really necessary?" asked Diane Ramirez, CEO of Halstead, a New York real estate company with thousands of agents, speaking to The New York Times. "I'm thinking long and hard about it. Looking forward, are people going to want to crowd into offices?"

The country's biggest tech firms have been instrumental in adapting quickly to the new normal.

Facebook CEO Mark Zuckerberg told employees that they could work from home into 2021. Google extended its remote working schedules until the end of the year. And Twitter CEO Jack Dorsey said in May that employees can work from home "forever".

But Tim Cook, CEO of Apple, told a virtual conference in September: "I can't wait for everybody to be able to come back into the office. I don't believe that we'll return to the way we were because we've found that there are some things that actually work really well virtually."

While CEOs question how they will operate post-pandemic, employees have embraced working at home, even though some said they feel isolated.

A Wells Fargo/Gallup poll found that 42 percent of the 1,094 workers it interviewed in August had a positive view of working remotely, compared with just 14 percent who thought it was negative. Mothers juggling child care and home schooling also said they were coping with multitasking.

A third of 1,200 office workers polled by PwC in June said they would prefer to never return to the office.