To avoid inconsistencies in median income figures for the same population as presented in different reports, all medians for family and household income in the 1980 census are based on the same set of 17 categories available on summary tape files, regardless of the number of intervals shown in various printed tables. Thus, the median shown in a report is frequently more precise than one the user could compute from the intervals shown in the report. Pareto interpolation is used rather than linear interpolation when the width of the income interval is more than $2,500.
For families and unrelated individuals, the median income is based on the distribution of the total number of families and unrelated individuals; whereas for persons, the median income is based on the distribution of persons 15 years old and over with income.
When the median income falls in the terminal category of a distribution, the method of presentation in reports is to show the initial value of the terminal category followed by a plus sign; thus, for example, if the median income falls in the terminal category "$50,000 or more," it is shown as "$50,000 +"in reports or as "$50,001" on STF's.