The number of cases on file as of February 1998 are estimated to represent about 85 percent of the final total for the year. The combination of the two sources has been used for a number of years to produce fairly accurate estimates of detailed traffic fatality statistics months before the actual reporting of all cases is completed. The estimates of fatalities for 1997 represent an extrapolation of the data presently available in the FARS file. Extrapolation factors have been established for each of the twelve months using the expected final monthly fatality counts and the corresponding counts in the FARS file. Past experience has shown that most large estimates, counts of 10,000 or more, tend to be within one percent of the final figure.
Smaller estimates are subject to relatively larger estimation errors.
For some data elements, e.g., Highway System, Land Use, Speed Limit and Vehicle Type, the reporting is not quite as complete at this early date and the file contains a large number of cases with unknown values. Additional adjustments were required for these data elements, in order to make proper comparisons with previous years' data. Sampling errors represent the probable differences between the results obtained from the sample survey and those results that would be obtained from a census of the population. Only FARS estimates of total fatalities in each state and region are presented in the report. The report presents a series of estimates on crashes, injuries, and fatalities for 1997.