A large empirical literature uses historical weather-yield relationships to assess the potential impacts of climate change on agricultural production. Technological change, however, may alter the sensitivity of agricultural production to climate stress in ways not fully captured by the simple time trends commonly used in empirical models. This paper examines whether climate-yield relationships in US corn production exhibit structural changes following the commercialization and widespread diffusion of biotechnology traits. Using county-level panel data on corn yields and weather variables from 1950–2024, we estimate fixed-effects models incorporating a structural break in 2003, corresponding to the commercialization of rootworm-resistant biotechnology traits in US corn production. The analysis incorporates alternative drought measures, precipitation controls, and nonlinear climate specifications. The results provide consistent evidence that corn yields became less sensitive to heat stress, drought conditions, and precipitation variability after 2003. The findings remain robust across alternative model specifications and structural break years between 2001 and 2005. Overall, the results suggest that technological advances may have altered historical climateyield relationships, with important implications for climate-impact assessments and projections of future agricultural damages.
