Core–periphery dynamics in the Portland, Oregon, region: 1982–2006

The relative strength of positive and negative spillovers of urban development is a long-standing and contested issue in regional and development economics, and the search for spread and backwash effects of development in urban core economies goes back at least 50 years. Using data from IMPLAN and the Bureau of Economic Analysis to develop multiregional input–output models, we developed estimates of core–periphery economic interdependence (sales and purchases of goods and services and commuting of workers between the core and the periphery) of the Portland, Oregon, region for 1982 and 2006. We explored whether the changing flows of sales and purchases, spillovers and commuting between 1982 and 2006 suggested a dominance of spread effects or backwash effects. We found increased commuting between periphery and core, decreased core–periphery transactions, and smaller core-to-periphery spillovers and periphery-to-core spillovers in both goods and services. Our findings do not point to a clear dominance of spread or backwash effects. Results showing smaller core-to-periphery and periphery-to-core multipliers/spillovers suggest that spread effects related to trade in goods and services weakened between 1982 and 2006. Our findings of increased commuting are consistent with enhanced spread effects in labor markets.