The world’s top investment banks are embarking on an enormous controlled experiment that will help determine the future of the office.

On one side, there are most of the big Wall Street banks, which have told employees they will soon be expected back in the office, pretty much as before. On the other side, there are the European banks, which are taking a much more flexible approach to continued home working. Whatever the outcome of the experiment, making the wrong call could prove a damaging mistake.