The other large exporters are HVAC and building control systems, followed by bio-fuels, green consumer products, air and water purification technologies, green chemicals and organic food (Brookings Institution, 201 lb). Prominent city indexes increasingly include sustainability as a factor of attractiveness or specifically rank cities by their "green-ness”, including the Siemens Green City Index, Forbes World’s Smallest Cities. The Chicago Tri-State metro-region has the potential to build on its reputation as a leader in innovative architecture and green building design. To sustain this reputation, there is a need to increase the scale of efforts like the City of Chicago’s green roofs and alleyway re-paving initiatives.