  In this paper we present a new method to trace the flows of phosphate from
the countries where it is mined to the countries where it is used in
agricultural production. We achieve this by combining data on phosphate rock
mining with data on fertilizer use and data on international trade of
phosphate-related products. We show that by making adjustments to data on net
exports and by estimating weighting factors we can derive the matrix of
phosphate flows on the country level to a large degree and thus contribute to
the accuracy of material flow analyses, a results that is important for
improving environmental accounting, not only for phosphorus but for many other
resources.
