There are many ways to measure resource availability. Although none are perfect, some are better than others. This chapter first considers measures that are entirely or largely physical in nature. These measures are frequently encountered in the literature and have considerable intuitive appeal. It then reviews measures that are economic in nature. Although all the economic measures have shortcomings, we will see that they are more useful than physical measures for assessing the long-run threat from mineral depletion. In Chapter 4, as a result, we will rely on economic measures to identify the historical trends in mineral commodity availability.
The logic behind physical measures is both simple ...