1. The U.S. Geological Survey has published a report on the historical prices on many metals in the United States over a 40-year period.
   
   Summarize the historical price trends (in constant dollars) for aluminum, copper, iron ore, mercury, and silicon. Would you conclude that the price of these non-renewable resources has increased or decreased over time? Do your findings support or refute Hotelling's rule? Explain. What factors may affect the prices of these resources?
   
   
2. Read the paper "Three General Policies to Achieve Sustainability," by Robert Costanza, Director of the Maryland International Institute for Ecological Economics.
   
   What are the three environmental policies advocated by Costanza? Summarize how a natural capital depletion (NCD) tax would work. Why does Costanza suggest that a NCD tax should be welcomed by both technological optimists and skeptics? What are environmental assurance bonds? Why are environmental assurance bonds a way to deal with the uncertainties of estimating environmental externalities?