Zillow CEO Rich Barton recently tweeted that he was giving all employees the option to work from home for the rest of 2020. “My personal opinions about WFH (work from home) have been turned upside down over the past 2 months. I expect this will have a lasting influence on the future of work … and home.”

Barton’s epiphany about working from home — echoed by other U.S. business leaders — may mark a decisive shift toward pervasive telework in the post-pandemic economy. Before COVID-19 appeared, just five percent of the U.S. workforce worked remotely full-time. Now, thanks to America’s extensive digital infrastructure, two-thirds of employees are working from home.

Some companies say they have witnessed an immediate bump in productivity as workers save time on commuting and have fewer in-office distractions. The temporary switch to remote work has gone so well at Twitter that the company has decided to make it the permanent default for most employees. Other tech companies may soon follow suit.

But before too many companies go all in on work from home, there is an important reason for caution: the current increase in productivity may be an illusion.