Summary results for country level and regional models to predict the spatial price index (price divided by the national average) for urea and cross-validation results: Pearson’s correlation coefficient between observed and predicted data price.

EI: Root mean square error (USD kg-1). E0: Mean square error of the Null model. ER: Relative mean square error, calculated as: 1-(EI / E0). EI and E0 are expressed for the relative index and for the relative index multiplied by the national average price (USD kg-1, values between parenthesis). For country-level models the data source was Africa Fertilizer, except where indicated otherwise.