Changes in Commodity Marketing Year Highs Over Time

Our market advisor periodically publishes a histogram that shows how many times a marketing year high in corn or soybeans has occurred in each month, starting with the 1970/1971 marketing year.

I won’t republish their exact chart, but this graph is created using the same data.

Full data set since 1970

The last time I looked at their histogram, I noticed how many of the data points in the September corn column were from the 1970s and 1980s. A lot has changed since then- South American production, changing weather patterns, more information technology at the USDA- and I wondered if the timing of the marketing year highs have shifted over time.

This was hard to visualize in their histogram, so I typed the data into my own spreadsheet and made a split bar graph to compare 1980-1999 with 2000-2019.


Nothing wildly different here. The most notable change is the decrease in highs in September and the increase in July.


For consistency with the first corn graph provided, here’s a soybean graph starting at 1970.

Then here’s the 20 year comparison.

If you’d like to approach this soybean chart with a South American narrative, it will support it. In the last 20 years you see a flattening of the seasonal pattern and the emergence of a few highs in January and March.

Raw Data

Attached is a CSV of the data if you’d like to dig deeper. This is technically cash price data for central Illinois so there could be some basis slippage to board prices.

Note: the Crop Year column is a single year and refers to the first year in the marketing year. (2020 Crop Year = 2020/2021 Marketing Year). I prefer working with 1 year in the raw data and converting back to a readable form as needed.

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