Illegally manufactured fentanyl kills a significant number of people in the United States and Canada every year. Since the emergence of modern heroin markets in the late 1960s, controlling supply has been associated with important reductions in opioid use and harms in several cases worldwide. But these efforts depend on understanding the dominant drug-trafficking routes.
In a new analysis, researchers developed an index to compare U.S. counties’ proportion of large seizures against their proportion of the national population. Their findings counter some assumptions about the origins of and routes into the United States of illegally manufactured fentanyl.
The analysis, conducted by researchers affiliated with Carnegie Mellon University, appears as a Manhattan Institute report.
“Efforts to counter drug flows need to be grounded in data,” explains Jonathan Caulkins, professor of operations research and public policy at Carnegie Mellon’s Heinz College, who coauthored the report. “Our analysis contradicts views—such as those used to justify certain tariffs—that treat the flows across the southern and northern borders as being comparably important.”
Border counties collectively show significantly higher rates of large fentanyl seizures than do counties in the interior. The authors define large as more than a kilogram of powder or more than 1,000 pills, quantities indicative of wholesale trafficking.
To determine which U.S. counties look like import or transit centers, the authors developed a disproportionality index, using data on fentanyl in 2023 and 2024; the index compares a county’s proportion of large seizures against its proportion of the national population. Drugs seized could be in transit to other places or they might be intended for local consumption, so it is useful to contrast a county’s share of large seizures with its share of the population, which serves as a proxy for the size of the local market.
Counties along the Mexican border account for only 2.35% of the U.S. population, but in 2023-2024, they hosted about 40% of the nationwide quantity of fentanyl appearing in large seizures, for both powder and pills, the analysis found. In contrast, counties in the lower 48 states that border Canada account for 3.1% of the U.S. population but only 1.2% of the powder and just 0.5% of the pills obtained in large seizures.
These findings can guide what policymakers should consider priority targets in efforts to control supply. Among the authors’ suggestions:
“U.S. counties along the Canadian border are not an important part of this story,” says coauthor Bishu Giri, an alumnus of Heinz College who is a data scientist specializing in natural language processing, machine learning, and geospatial analysis. “Our findings call into question tariffs and other policies and policy justifications that treat the threat from the northern border as comparably severe to that from the southern border.”
Fentanyl at the Gates Comparing Large Seizures at the U.S.–Mexican and U.S.–Canadian Borders
1-Jul-2025