Â鶹ÒùÔº

Considerations related to environmental justice have risen to the forefront of policy discussions over the location of long-term infrastructure like power plants. These discussions have centered on ensuring equitable siting of planned infrastructure, but rarely account for its consequences over the long run.

In a , researchers examined the relative contributions of siting decisions (i.e., where to locate infrastructure projects) and demographic shifts after projects are built to current disparities in exposure to polluting U.S. fossil fuel plants. The study found little evidence that plants were disproportionately located in counties with higher Black populations, on average. But it also found that the share of the Black population grew in the decades after the first fossil fuel plant was built in a county.

The study was conducted by researchers at Carnegie Mellon University, Arizona State University, Université de Montréal, and Boston College. It will be published in this year's NBER volume, titled "Environmental and Energy Policy and the Economy."

"Relatively little research has focused on estimating social lifecycle impacts of long-lived infrastructure because the effects can take many decades to show up," says Karen Clay, professor of economics and public policy at Carnegie Mellon's Heinz College, who led the study. "Our work highlights that the equity implications of siting long-lived infrastructure can differ significantly depending on the time period studied."

Researchers leveraged newly digitized data on the siting of power plants and their operations from 1900 to 2020, combined with spatially resolved demographics and population data from the U.S Census from 1870 to 2020. This extended time horizon allowed them to assess how demographics evolve over several decades after power plants are built.

The study also collected data on the potential determinants of power plant siting over time (e.g., population, transmission infrastructure, location of coal production, economic activity, railroads), which allowed researchers to determine the potential role played by pre-existing demographics in addition to other siting determinants.

Researchers found little evidence that power plants were sited disproportionately in counties with a higher share of Black residents, on average. Instead, siting decisions appear to have been influenced primarily by factors related to local demand for electricity and operating costs. The plants tended to be disproportionately located in counties that were more populous, had larger employment shares in manufacturing, and enjoyed better access to coal.

But researchers also discovered that openings of fossil fuel power plants led to long-term increases in counties' shares of Black populations, with an average rise in Black population share of 4% in the 50 to 70 years after the first plant was built. These longer-run demographic responses to early power plant openings likely reflect a number of interrelated mechanisms, the authors conclude, such as the Great Migration and local sorting within and across county boundaries based on air pollution and other factors.

Between 1910 and 1970, millions of African Americans moved from the South to northern cities, population inflows that resulted in large outflows of white people from city centers to outlying suburbs and neighboring counties, especially between 1940 and 1970.

This historical evolution in the local costs and benefits of fossil fuel power plants underscores the importance of quantifying the short- and long-run demographic changes that follow power plant siting, suggest the authors. Long-term demographic shifts after siting likely play a much larger role in current disparities in power plant exposure than does inequity in initial siting decisions. In this way, even when plants are not sited inequitably, geographic mobility can lead to inequitable outcomes.

"Our findings have important implications for infrastructure investment, particularly in the context of environmental justice," says Akshaya Jha, associate professor of economics and public policy at Carnegie Mellon's Heinz College, who coauthored the study. "Because the equity implications of investments in long-lived infrastructure vary depending on the time period studied, it is essential to consider the full social life cycle of these investments to ensure equitable outcomes."

"While infrastructure projects like fossil fuel plants may promise short-term economic or energy benefits, their long-term implications often extend far beyond immediate gains," adds Noah Miller, postdoctoral research fellow in public policy and management at Carnegie Mellon's Heinz College, who co-authored the study. "The persistence of these disparities points to the need to incorporate a long-term perspective into decisions about infrastructure planning and policy."

The authors note that their analyses were done at the county level, so they likely underestimate the full demographic shifts after siting of power plants.