Contra conventional wisdom, new hybrids don't seem to be moving the corn trend line. In fact, there isn't one right now.
This is less unusual than it might seem.
Statistical analysis finds no statistically significant time trend in average U.S. corn yields since 2003. Thus, the increase in consumption of U.S. corn from 10.2 billion bushels to 12.6 billion bushels between the 2003/04 and 2011/12 crop years, has largely been met through an increase in planted acres of 13.3 million (from 78.6 million acres to 91.9 million acres).It is much harder to come up with some sort of composite (rain, heat, delays, etc.) weather graph that shows a trend is weather influence. But my bet it it would not be flat like the above.
It is important to note that it is not uncommon to find no statistically significant trend in U.S. average yield over a 9 year period. Of all 64 9-year periods starting with the 9 years that begin in 1940, less than half had a statistically significant upward trend in corn yields. This may seem surprising since the average annual increase in U.S. average corn yields since 1940 is 2.2% per year. [More]
There are many of us with a downward 9-year trend since 2003. Those who have had some spectacular crops in the last few years may be misled into thinking the curve always goes up.
At the very least, the assumption of unlimited productivity advances looks a little shaky to me.