The situation is improving however, as average pollutant levels have decreased fairly steadily over the past decade (CMAP, 2010a). Suburbanisation continues to occur in the region: the Chicago Tri-State metro-region is among the top 20 OECD regions in terms of growth of the suburban belt relative to the urban core (Figure 1.14).15 The suburbanisation of housing has been met by the suburbanisation of employment: between 1960 and 1990, over 96% of new jobs in the region were created outside downtown (Chicago Council on Global Affairs, 2007, CMAP, 2010a). Low levels of housing and employment densities in the suburbs have resulted in an auto-dependent built environment in which the provision of transit services is inefficient and cost-prohibitive. Chicago here refers to the Tri-State Chicago metro-region which corresponds to the Metropolitan Statistical Area (MSA). Source: OECD Metropolitan Regions Database and OECD Regional Database. Public transportation accounts for just 2.5% of daily commuting in the Chicago Tri-State metro-region (9% in the seven counties of the CMAP area) (CMAP, 2010a).