Leadership in Energy and Environmental Design (LEED) is a green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council (USGBC), it includes a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighborhoods, which aims to help building owners and operators be environmentally responsible and use resources efficiently. By 2015, there were over 80,000 LEED-certified buildings and over 100,000 LEED-accredited professionals. Most LEED-certified buildings are located in major U.S. metropolises. LEED Canada has developed a separate rating system adapted to the Canadian climate and regulations. Some U.S. federal agencies, state and local governments require or reward LEED certification. This can include tax credits, zoning allowances, reduced fees, and expedited permitting. Studies have found that for-rent LEED office spaces generally have higher rents and occupancy rates and lower capitalization rates. LEED is a design tool rather than a performance-measurement tool and focuses on energy modeling rather than actual energy consumption. It lacks climate specificity, and has been criticized for a point system that can encourage inappropriate design choices and make energy conservation the weakest part of the evaluation. It has also been criticized for the phenomenon of "LEED brain" in which the public relations value of LEED certification drives the development of buildings. History Development of the Leadership in Energy and Environmental Design (LEED) certification program began in 1993, spearheaded by Natural Resources Defense Council (NRDC) senior scientist Robert K. Watson and supported by the U.S. Green Building Council (USGBC). Among the contributors to the initial guidelines were J. D. Polk, co-founder of Solar Cells, Inc. (now First Solar), and solar-power advocate Lawton Chiles, the Governor of Florida at the time. Watson led a broad-based consensus process for two decades, bringing together non-profit organizations, government agencies, architects, engineers, developers, builders, product manufacturers and other industry leaders. The USGBC Board of Directors was chaired by Steven Winter from 1999 to 2003. At that time, USGBC's Senior Vice President of LEED, Scot Horst, became chair of the LEED Steering Committee before joining USGBC staff. Early LEED committee members also included USGBC co-founder Mike Italiano, architects Bill Reed and Sandy Mendler, builders Gerard Heiber and Myron Kibbe, and engineer Richard Bourne. As interest in LEED grew, engineers Tom Paladino and Lynn Barker co-chaired the LEED technical committee, formed . From 1994 to 2015, LEED grew from one standard for new construction to a