By 1906, Sears, Roebuck and Co had opened their mail order and headquarters operation in a 3,000,000-square-foot (Template:Convert/LoffAonSon) building in Chicago, at the time the largest building in the world. The time and motion study, pioneered in manufacturing by F. W. Taylor and later applied to the office environment by Frank and Lillian Gilbreth, led to the idea that managers needed to play an active role in directing the work of subordinates in order to increase the efficiency of the workplace. F.W. Taylor advocated the use of large, open floor plans, and desks that faced supervisors. As a result, in 1915, the Equitable Life Insurance Company in New York City introduced the “Modern Efficiency Desk” with a flat top and drawers below, designed to allow managers an easy view of the workers. This led to a demand for a large square footages per floor in buildings, and a return to the open spaces that were seen in pre–industrial revolution buildings.