The Energy Information Administration (EIA), in preparing model forecasts for its Annual Energy Outlook 2005 (AEO2005), evaluated a wide range of current trends and issues that could have major implications for U.S. energy markets over the 20-year forecast period, from 2005 to 2025. Trends in energy supply and demand are linked with such unpredictable factors as the performance of the U.S. economy overall, advances in technologies related to energy production and consumption, annual changes in weather patterns, and future public policy decisions [see endnote 1 on page 8]. Among the most important issues identified as having the potential to affect the complex behavior of the domestic energy economy, oil prices and natural gas supply were considered to be of particular significance in increasing the uncertainty associated with the AEO2005 reference case projections.