"raising the intensity of corn-seed/acre by 2%-3% per year" — There's a limit there, if only for the need for space to allow fertilizers and sunshine.
Sunlight can be a limiting factor in the spacing of soybeans because a shade canopy creates practical problems. For corn, water is more likely than sun to be a limiting factor; the 2-3% increase in crop density cited in #msg-50378397 can often be accomplished without overspending the water supply via improvements in the smartness of the irrigation systems. As mentioned in #msg-50378397, high-tech improvements in tractors and combines from such companies as DE allow a higher “resolution” of the farm grid that makes it possible for farmers to consider an increase in crop density.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”