Our sensitivity analysis starts with an explicit representation of un­ certainties about the inputs through the specification of probability distributions over the input parameters. Wherever possible, we try to specify ranges for these distributions that span the forecasts by other organizations, such as the Energy Information Administration (EIA), Data Resources Incorporated (DRI), the Electric Power Research Insti­ tute (EPRI), and the North American Electricity Reliability Council (NERC). Where sources for parameter specifications are not other­ wise indicated, the choices reflect our own judgment.