of this decentralization for urban form. The first and dominant view, according to Lee (2007), holds that metropolitan areas are polycentric, increasingly characterized by the presence of multiple activity nodes or employment centers. The second view (Glaeser and Kahn 2001; Lang and LeFurgy 2003) holds that suburban employment should be conceived of as being dispersed, not polycentered (Glaeser and Kahn 2001). Lang and LeFurgy (2003) provide data that support the second view, at least as it relates to the dispersion of office space. In 13 of the nation’s largest office markets, for example, most metropolitan rental office space exists either in high-density downtowns or in low-density edgeless cities, not in employment centers outside the CBD.13
Understanding employment patterns, particularly the factors that lead to the formation of employment centers outside the CBD, has particular relevance for the present study. Travel patterns are influenced by the density of commercial as well as residential development, particularly the density of development at the job end of the daily commute (Cervero and Duncan 2006). Of particular interest is whether jobs are clustering outside of the center city in aggregations large enough to support transit; encourage mixed-use development near job sites within walking distance; or facilitate shorter automobile trips because jobs are located closer to residents, thereby improving the jobs–housing balance.
A review of the literature in a paper commissioned for this study (Giuliano et al. 2008) finds support for the view that decentralization of employment in metropolitan areas has resulted in new agglomerations outside the CBD. The presence of employment centers is demonstrated across metropolitan areas of varying size, age, location, and growth rates (see Table 8 and discussion in Giuliano et al. 2008). Nevertheless, the authors note that, despite the presence of these centers, most metropolitan employment is dispersed; the share of employment outside centers is on the order of two-thirds to three-fourths (Giuliano