Per-region OLS: target stocks = f(x1, year, x3). For non-Dec: x1 = prev quarter stocks − exports. For Dec: x1 = Sep stocks + production − exports. Exports = FGIS inspections summed over inter-quarter months (up to 2 export regions searched). x3 = best residual predictor from ~28 candidates (yield dev, acres, on/off farm ratios, etc.).