Corn and soybean futures typically move about 0.4-0.5% on an average WASDE surprise — and the size of the surprise reliably predicts the size of the move

Summary

USDA's monthly WASDE report moves corn and soybean futures by roughly half a percent on average, but with substantial spread: the standard deviation of the reaction is about 1.9% for corn and 1.5% for soybeans, and individual releases have swung prices as much as 6-7% in either direction (or tens of cents per bushel intraday, as in several recent examples below). Yes, the size of the surprise (the gap between USDA's number and the pre-report analyst consensus) does predict the size of the move: a 1% surprise in USDA's US ending-stocks estimate is associated with roughly a 0.11-0.13% move in corn futures and a 0.06-0.07% move in soybean futures, and this relationship is statistically significant at the 99% confidence level. Corn is consistently more sensitive to surprises than soybeans, and the market reacts far more to the US-specific numbers in the report than to the global/world figures it also contains.

Why this corpus alone could not answer it

The AskAmerica warehouse was checked first, as required. It has no futures-price table (sec.stock_prices covers equities/Stooq data, not CME futures contracts) and no WASDE table at all — search_catalog returned 'wasde' as an unmatched term against every schema and column in the corpus. The ag schema carries USDA NASS crop production, land values, and farm income, but not the monthly WASDE supply/demand estimates or futures market data needed to build a surprise-vs-price-move regression internally. This is a genuine, confirmed coverage gap, not a query that needed retrying — the answer below is built entirely from primary academic sources and market-commentary sources fetched and read directly.

How big is the average move?

The most directly on-point source is Blazzard, Anderson & McKenzie (2026, Journal of Agricultural and Applied Economics), which studied all 129 WASDE releases from 2013-2023 using CME nearby futures prices and Bloomberg median analyst forecasts as the pre-report expectation benchmark. Key descriptive statistics for the noon-to-close price change on WASDE release day:

• Corn: mean change +0.06%, standard deviation 1.91%, range -6.57% to +6.20%
• Soybeans: mean change -0.08%, standard deviation 1.49%, range -5.69% to +4.40%

The mean is near zero because surprises are unbiased in direction (sometimes bullish, sometimes bearish), but the standard deviation and range show that individual releases regularly move prices by 1-2%, and occasionally by 5-7%. This is corroborated by Sumner & Mueller (1989), an older study of 1961-82 data, which found daily price changes in a similar -0.11% to +0.13% range on report days — the magnitude of the reaction has been stable across five decades of USDA reports.

Two concrete recent examples illustrate the range: the January 2026 WASDE (a much-larger-than-expected corn crop, stocks-to-use up to 13.6% from 12.5%) sent March corn futures down 26 cents (from $4.474 to $4.214/bu, about -5.8%) and March soybean futures down 20.2 cents (from $10.692 to $10.49/bu, about -1.9%) by close (Rabinowitz, Southern Ag Today 2026). By contrast, the September 2025 WASDE moved new-crop corn futures down as much as 6 cents/bushel and soybeans down as much as 13 cents/bushel in the 15 minutes immediately after release, before other-day trading reversed much of that move and both contracts actually closed UP on the day (Janzen, farmdocdaily 2025) — illustrating that the immediate 15-minute reaction and the full-day reaction can sometimes diverge sharply, though Janzen documents this as rare (only 2 other such divergences among the six 2025 report releases he examined).

Separately, Mattos & Silveira (2016) found that USDA reports increase the conditional standard deviation (a volatility measure, not a mean price change) of corn futures returns by 28.13% during the August-October period and by 11.91% the rest of the year — confirming that report days are unusually volatile even when the average price change looks modest. Adjemian & Irwin (2018) separately show that since floor-trading halts around report releases were eliminated in 2012, the volatility spike from a report hits within minutes of release and dissipates within a few more minutes of continuous trading — the reaction is fast, not spread out over the day.

Does the size of the surprise predict the size of the move?

Yes. Blazzard et al. define 'surprise' as the percentage gap between the WASDE's US ending-stocks estimate and the pre-report median analyst forecast, then regress the futures price change on that surprise (Seemingly Unrelated Regression, corn and soybeans jointly, intercept fixed at zero). Across all model specifications:

• Corn: a 1% higher-than-expected ending-stocks surprise is associated with a -0.117% to -0.127% price change (statistically significant, p<0.01, in every specification)
• Soybeans: a 1% surprise is associated with a -0.061% to -0.066% price change (also significant, p<0.01, in every specification)

The negative sign matches basic supply-and-demand logic: higher-than-expected ending stocks (more supply than the market priced in) push futures prices down. Averaging the actual surprise sizes seen over the sample (surprises average roughly 0.3-1% in magnitude, with standard deviations of 6.4 points for corn and 10.4 points for soybeans, and ranges as wide as -33% to +45% for soybeans), the authors compute an average total price effect per report of about 0.52% for corn and 0.42% for soybeans from the US surprise alone. Corn futures are consistently more sensitive to a given percentage surprise than soybean futures are — the authors attribute this partly to the smaller share of US corn production that is exported (14%) versus soybeans (47%), meaning world market conditions dilute the US-specific signal less for corn.

By contrast, surprises in the world (global) ending-stocks figure in the same WASDE report were not statistically significant predictors of US futures price moves in most model specifications — the market treats USDA as a credible source for domestic US supply data but reacts much less to the WASDE's global aggregate numbers, which are built from lower-quality international data. The January 2026 example is a real-world illustration of the relationship: the corn crop surprise (269 million bushels above the prior month, a large surprise) produced the much larger price move (-5.8%), while the smaller soybean supply surprise (17 million bushels above expectation) produced the smaller price move (-1.9%) — consistent with corn's larger regression coefficient and generally larger surprise-to-move ratio. The September 2025 example shows the relationship is not mechanical minute-to-minute: a large corn acreage surprise (1.4 million more acres than expected) was offsetting a smaller-than-feared yield cut, so the net 'surprise' to the balance sheet was smaller than the acreage number alone suggested, and traders revised their reaction accordingly within the day.

Caveats

The regression coefficients (-0.117 for corn, -0.061 for soybeans) describe the AVERAGE relationship across the whole 2013-2023 sample; a single month's move can deviate from this because of confounding same-day news, weather, or macro shocks the model does not control for, and because markets sometimes judge a headline number as already stale relative to newer information (as in the September 2025 example). The sample is limited to 129 monthly observations (the post-2012 period after floor trading pit closures ended a different price-change measurement convention), so the confidence intervals, while statistically significant, are not enormous-sample precision. Also, 'surprise' here is measured against the analyst median just days before release, not the market's exact real-time expectation, so it is a good but imperfect proxy for what the market didn't already know.