Project Overview
This project extends ecologically unequal exchange (EUE) theory to the subnational level, asking whether the dynamics observed between nations where net exporters of ecologically intensive goods bear disproportionate environmental costs also operate across US counties. Using the Commodity Flow Survey (CFS) for 2012, 2017, and 2022, the study constructs a directed inter-county shipment network and derives four original measures capturing different dimensions of counties' ecological exchange positions. These are linked to EPA fine particulate matter (PM2.5) data in a county fixed-effects panel model.
Network Measures of Ecological Exchange
A central methodological contribution of this project is the development of four complementary network-based measures that capture distinct dimensions of a county's position within the ecology of commodity exchange. Rather than relying on industry classifications or production-side data alone, these measures are derived directly from observed shipment flows between counties, weighted by shipment value and survey weights. Ecologically intensive commodities are identified using SCTG codes covering minerals and ores (10-14), fossil fuels and petroleum products (15-19), chemicals and hazardous materials (20-24), and primary metals and heavy manufacturing (31-34).
1. Net Ecologically Intensive Exchange Position
Net balance of ecologically intensive flows. Positive = net sender; negative = net receiver. Normalized to [-1, 1] for cross-county comparability.
2. Eco-Intensive Inflow Dependence
Share of all incoming flows that are ecologically intensive. Captures structural linkage to ecologically intensive activity through what a county receives rather than what it produces.
3. Eco-Intensive Production Share
Share of a county's outgoing flows that are ecologically intensive. Higher values indicate that a larger share of what a county exports to the rest of the economy is environmentally burdensome production.
4. Transit & Warehousing Share
Share of outgoing flows from transportation and warehousing (NAICS 48-49). Identifies counties functioning as logistics intermediaries rather than production sites — a theoretically distinct ecological role.
Interactive Maps: County-Level Network Measures (2022)
The maps below show the geographic distribution of each network measure across US counties in 2022. Use the buttons to switch between measures. Hover over any county to see its name and values.
Regression Results: Network Measures
The coefficient plot shows the estimated effect of each network measure on county PM2.5 from the full fixed-effects model (Model 4), which includes all socioeconomic controls, county fixed effects, and year fixed effects. Error bars represent 95% confidence intervals.
Key Findings
The results provide consistent support for extending EUE theory to the subnational level. Net EUE position is positively and significantly associated with PM2.5 across all model specifications. Counties that are net exporters of ecologically intensive goods experience higher ambient PM2.5, even after absorbing all time-invariant county heterogeneity via fixed effects.
The negative coefficient on eco-intensive inflow dependence is theoretically coherent: counties that depend on receiving ecologically intensive goods from elsewhere are externalizing production costs to their trading partners. The transit and warehousing share coefficient is also negative and significant, distinguishing the environmental consequences of facilitating exchange from those of driving it.