U.S. ENERGY SOURCES AND USES The Energy Information Agency (www.eia.doe.gov) of the United States government contains a treasure trove of data about both U.S. and international energy generation and consumption. Go to the Historical Data Overview page at www.eia.doe.gov/overview_hd.html and notice the Energy Flow diagram that appears at the upper right. Click on the diagram to expand it and then look it over. The diagram gives energy consumption and usage for the United States for the most recent year for which data is available. Is the United States totally dependent on oil imports? What fraction of its oil consumption does it have to import? Is it strange that even though the country is a net importer of petroleum, it exports some petroleum, too? What about the overall energy situation? What percentage of its overall energy consumption can it fulfill with domestically produced energy? What fraction of domestic production comes from renewable energy sources? Is this higher or lower than you were expecting?

CARBON DIOXIDE EMISSIONS—RISING OR FALLING?
We presented evidence earlier that per capita consumption of water, energy, and solid objects like plastics and metals has been constant or falling in recent decades. The consumption of fossil fuels, however, is of special concern because of worries about global warming caused by the emission into the atmosphere of carbon dioxide and other so-called greenhouse gasses. Go to the Energy Information Agency's Environment page, www.eia.doe.gov/environment.html. Scan the International Emissions Data links and click on the one that says Per Capita Emissions in order to open up an Excel spreadsheet that contains per capita carbon dioxide emissions for almost all countries for each of the previous 20 years or so. Have per capita carbon dioxide emissions in the United States, Japan, and France grown, stayed about the same, or fallen over the past couple of decades? Does it surprise you to learn that over this time period France has moved to generate more than 80 percent of its electricity from nuclear power, which emits no carbon dioxide? What about emissions in China, Indonesia, and India? Why have emissions risen so much (in percentage terms) in these countries? (Hint: They are not as poor as they used to be.) If current trends in these countries continue, should we be worried? And could defining property rights over the atmosphere solve the problem?