The Proven Reserves of the Earth

The most common measure to discuss the abundance of resources is known or proven reserves. Proven reserves are quantities over resource that are definitively known to exist in particular locations and can be extracted with current technology and prices. Simon illustrates how these proven reserves have increased between 1950 and 1990 for some important industrial metals. The world's population in 1950 was around 2.5 billion people and by 1990 had grown to around 5.32 billion people. Measured in 2011 dollars, World GDP in 1950 is estimated to have been $9.25 trillion and $47.04 trillion in 1990. So in a forty-year period in which the human population grew by a multiple of 2.13 and in which human