The economic activity of a country is often quantified as the gross domestic product (GDP), which is the sum of private and government consumption, investments, and net exports (the value of exports minus the value of imports). For a developed country such as the United States, economists might see a GDP growth rate of 3% a year as reasonable. However, production and consumption create some pollution. By how much would pollution per dollar of GDP have to decline for pollution levels 50 years from now to be the same as current levels, assuming a 3% annual growth rate of GDP? In 75 years? In 100 years