Applying Hubbert Curves and Linearization to Rock Phosphate

Rock phosphate is a critical, nonrenewable resource for which there is no known substitute in agriculture. Cordell, Drangert, and White (2009) use Hubbert methodology (1956) to estimate the peak—the year after which production will monotonically decline—of world rock phosphate production at 2033–34. This note assesses the applicability of Hubbert's (1949) peak methodology to world rock phosphate production, based on (a) the ability of the model to produce accurate in-sample and out-of-sample forecasts and stable estimates of ultimately recoverable reserves, and (b) the degree to which the rock phosphate market approximates the theoretical conditions underpinning the Hubbert model. In both respects, the application of Hubbert methodology to rock phosphate is found to be problematic.