Fig. 1. Background of U.S. hybrid corn. Pedigree background frequencies for 33 Pioneer Hi-Bred International elite proprietary inbreds with parental background above and with publicly available representatives below; adapted from Smith et al. (1990).
Fig. 2. Average U.S. corn yields and kinds of corn, Civil War to 2003. The b values (regressions) indicate production gain per unit area per year; 2003 production with prehybrid yields requires an additional 130 million ha (320 million acres). Value doubles in 26 yr because higher yields allow low (0.5%) annual price increase. Data compiled by the USDA.
