From the original post:

"All of the seasonal charts are based on the 1992 to 2012 Time Period.

When analyzing these types of charts for patterns, it is more important to note the timing of market trend changes than to note the magnitude of the price change percentage."

The data is futures, not local cash, prices and the frequency of the data is weekly (closes).

The time period includes the pre and post ethanol and bio-fuels era.

The ethanol and bio-fuels era has likely led to a flattening of the range on the corn % changes, but has not eliminated the seasonal nature of price trends.

Ethanol has grown into a "fixed" variable over time as the industry has matured.

Adding a "fixed" or constant (ethanol) variable to fluctuating variables (other demand and supply) that are based on seasonal patterns still results in a fluctuating output (price).

Therefore, the fluctuating output (price) may be on a different base level, but it will still fluctuate with the seasons.