Office buildings across the U.S. are still pretty empty. In 10 major metropolitan cities, the average number of office workers who returned to their desks fell to 21.7 percent on Jan. 20, according to a new report by Kastle Systems International. Many companies are still taking a wait-and-see approach as coronavirus vaccinations continue their slow pace. American Express this week told workers to operate from home until Labor Day. In New York, occupancy fell to 12.9 on Jan. 20, from 14 percent the week before, the Kastle study found. Meanwhile, Manhattan’s office availability in the fourth quarter hit a record high of 14.3 percent, according to a recent report from Colliers International.