EIA's Monthly Energy Review (MER) and the underlying MER data upon which this report is based detail energy consumption data by fossil fuel and by sector. The total consumption amounts by fuel are obtained from various EIA surveys that feed the MER data series and reflect the most up-to-date information available. During the early months of the year, the division of total fuel consumption among the residential, commercial, industrial, transportation, and electric utility sectors for the prior year, as reported in the MER, is in some cases inferred on the basis of the division among sectors during the prior year. As additional information becomes available, the inferred division is replaced with the actual division. When the sectoral split does not vary from one year to the next, the use of the previous year's split does not introduce problems. Between 1997 and 1998, however, several important factors produced a shift in fuel consumption among the end-use sectors. Because 1998 was an unusually warm year, demand for heating fuel was lower than in 1997; thus, the residential and commercial sector shares of distillate and residual fuel oil consumption should also have been lower. At the same time, the economy grew rapidly, theoretically increasing fuel use in the industrial and transportation sectors.

The EIA publication Fuel Oil and Kerosene Sales 1998 contains the sectoral splits needed to adjust the MER data to reflect a shift in consumption among sectors for distillate and residual fuels. To provide a better estimate of the sectoral split in 1998, the data from the Fuel Oil and Kerosene Sales 1998 report were used in conjunction with the MER data. There are two data series in the report: actual and adjusted. The adjusted series matches the fuel totals from EIA's Petroleum Supply Annual (PSA). Because the MER totals also match the PSA totals, the adjusted data series was used, and the totals for fuel consumption and emissions remained the same as reported in the MER. The total amounts were then reallocated to the four end-use sectors for 1998 according to the amounts given in the Fuel Oil and Kerosene Sales 1998 report.