Are Crop Yields Becoming More Stable and Higher? Evidence from U.S. County-Level Data Since 1980

This brief examines how county-level yield volatility has evolved over time across major U.S. crops and discusses implications for crop insurance modeling. Using USDA NASS county yield data from 1980–2024 for corn, cotton, soybeans, and winter wheat, we construct normalized yield shocks under alternative detrending methods and compare volatility across two subperiods. Results show that yield volatility has generally declined for corn, cotton, and soybeans, while winter wheat remains relatively stable. Spatial patterns reveal substantial geographic heterogeneity, with the most pronounced reductions in yield volatility concentrated in core production regions that also exhibited stronger yield growth over the same period. These findings highlight the need to incorporate time-varying yield risk in insurance simulation frameworks.