Long-term projections of non-fuel minerals: We were wrong, but why?

In light of the data and analysis presented in Projected versus observed rates of growth in the production and consumption of selected minerals for the year 2000, Explaining the differences between the projected and observed levels of consumption of non-fuel minerals in the year 2000, the article concludes with some remarks, made almost a quarter of a century ago, by Prof. Leontief on the need and justification for long-term projections.