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Results for multiple linear regression models using non-standardized predictor variables aggregated across six world geographical regions (n = 30). a, A regression using effective crop group diversity. b, A regression using effective crop species diversity. Stability, μ and σ of caloric yield were log-transformed. Oceania is the reference region to which results for every other region is compared. *P < 0.05; **P < 0.01; ***P < 0.001.