Chris Hurt and fellow ag economists at Purdue University use trend yields when figuring crop budgets for 2013. They also used trend yields to project out through 2016. Using trend yields, they show a fairly stable crop production picture. Trend yields tend to bring more stable prices.
One of the things they can't anticipate is weather extremes that might alter yield. And while this is Indiana yield, most of the time, if Indiana yield is way off one way or the other, the national yield may be off, too, affecting prices.
A look back at Indiana's statewide average yield for the two crops since 2005 indicates that while over time the trend line holds, there has been a lot of variability lately. For example, the statewide corn average yields from 2005 through 2012 in bushels per acre are 154, 157, 154, 160, 171, 157, 146 and 100. That's an average of 149.5, hardly near trend yield in the 165 bushel per acre range. However, without last year, the year of the greatest deviation from trend yield in recorded history, the average is 157 bushels per acre. It's still below trend, indicating that there have been some up and down weather years over the last decade.
Soybean yields show a similar picture. Actual statewide average yields since 2005 are 49, 50, 46, 45, 49, 48.5, 45 and 41 bushels per acre. While the trend seems downward, the last three summers have featured dry periods during the reproductive phase over much of the state. The overall average over the last 8 years for soybeans in Indiana is 46.7 bushels per acre. The average of just the past three years is 44.8 bushels per acre. Soybeans are much more consistent and vary less, even in stress years, than corn based on historical data such as this taken over the last eight years.