How concentrated are US import sources compared with Europe and China?
Core argument: The US has the highest Herfindahl-Hirschman index for total imports among the three big regions in every year examined, though its sourcing has become more diversified since 2018.
The Herfindahl-Hirschman index (HHI) is calculated as the sum of squared market shares. The higher the HHI, the greater the concentration of import sources; a lower HHI indicates more variety. The US index for total imports is the highest of the three regions for every year examined. Only four trading partners each supply the United States with more than 10% of its total imports—the European Union, Canada, Mexico, and China—but diversification of its sourcing has increased since 2018. China’s import sourcing is the most diverse of the three big regions; its concentration index is substantially lower than those of the other two, figure 1 shows. Only the European Union provides more than 10% of the total value of China’s imports.

