There are any number of which we have "only X years of proven reserves left", for which we've had X years left for 3X years. That's because mining companies onl

There are any number of which we have "only X years of proven reserves left", for which we've had X years left for 3X years. That's because mining companies only prove out reserves for many ores only as far in advance as necessary to show they are a viable concern to invest in. 99.99% of the earth's crust has never been explored. When oil got scarce on land in temperate climates, companies began looking -- and finding -- oil in cold, tropical, and ocean environments. Then there's the very real possibility of substitution by other technologies. No doubt there were those who predicted the world would run out of silver for developing photos. Now we have digital photography getting better all the time. And dont' get me started in carbon nanotube technology. And finally, why didn't they include the numbers for iron? (Over 1,000 years worth proven.)