The total factor productivity index for u.s. wheat was 1.5% per year between 1974 and 1983. The conservation tillage productivity index for u.s. wheat was about 1.1% per year during this time period, or about 75% of the T.F.P. North Dakota and Washington were equal in competitive advantage in 1983. Scale economies in u.s. wheat production represented between a six and two percent advantage for very large (2700 acres) and large (1100 acres) enterprises over medium size (650 acres) enterprises in 1983.