They are also inter-related: for example, lower availability of a natural resource may increase prices, which in turn may mean that a previously unprofitable technology is now considered viable.
[3] The diagram was introduced in 1972 by American geologist Vincent Ellis McKelvey, the 9th Director of the United States Geological Survey.
[6] An even more minimalist version than the original, referred to as the Total Resource Box, has been "simplified and modified to make it more understandable to politicians and laypersons.
"[11] The Society of Petroleum Engineers (SPE) has built upon the McKelvey diagram for use in the fossil fuels industry.
[15][16][17] The United Nations Framework Classification for Resources (UNFC) incorporates elements from the McKelvey diagram and other systems.
The UNFC dimensions are: (E) Economic and commercial viability, (F) Field project status and feasibility, and (G) Geological knowledge.