This is complemented by specialisation in air and water purification technologies. Both activities reflect the strength Milwaukee Water Council, which advances the interests of more than 150 companies and research institutions located in the greater Milwaukee region, that produce water-related goods, services, or research. These segments do not include suppliers to green companies, thus potentially understating the size of green clusters in the metro-region. Specialisation ranking among US metro-regions: the numerator is the ratio of jobs in the segment and metro-region in 2010 to total metro-region employment in 2010. Total does not include public transit or waste management. These segments do not include suppliers to green companies, thus potentially understating the size of green clusters in the metro-region.