The median divides the income distribution into two equal parts: one-half of the cases falling below the median income and one-half above the median. For households and families, the median income is based on the distribution of the total number of households and families including those with no income. The median income for individuals is based on individuals 15 years old and over with income. Median income for households, families, and individuals is computed on the basis of a standard distribution (see the "Standard Distributions" section under "Derived Measures"). Median income is rounded to the nearest whole dollar. Median income figures are calculated using linear interpolation if the width of the interval containing the estimate is $2,500 or less. If the width of the interval containing the estimate is greater than $2,500, Pareto interpolation is used. (For more information on medians and interpolation, see "Derived Measures".)

In compiling statistics on family income, the incomes of all members 15 years old and over related to the householder are summed and treated as a single amount. Although the family income statistics cover calendar year 1999, the characteristics of individuals and the composition of families refer to the time of enumeration (April 1, 2000). Thus, the income of the family does not include amounts received by individuals who were members of the family during all or part of calendar year 1999 if these individuals no longer resided with the family at the time of enumeration. Similarly, income amounts reported by individuals who did not reside with the family during 1999 but who were members of the family at the time of enumeration are included. However, the composition of most families was the same during 1999 as at the time of enumeration.

Own child is a never-married child under 18 years who is a son or daughter of the householder by birth, marriage (a stepchild), or adoption. For 100-percent tabulations, 'own children' consist of all sons/daughters of householders who are under 18 years old. For sample data, 'own children' consist of sons/daughters of householders who are under 18 years old and who have never been married. Therefore, numbers of own children of householders may be different in these two tabulations since marital status was not collected as a 100-percent item in Census 2000.

In certain tabulations, own children are further classified as living with two parents or with one parent only. Own children living with two parents are by definition found only in married-couple families. In a subfamily, an "own child" is a child under 18 years old who is a natural-born child, stepchild, or an adopted child of a mother in a mother-child subfamily, a father in father-child subfamily, or either spouse in a married-couple subfamily. (Note: In the tabulation under "EMPLOYMENT STATUS" of own children under 6 years by employment status of parents, the number of "own children" includes any child under 6 years old in a family or a subfamily who is a son or daughter, by birth, marriage, or adoption, of a member of the householder's family, but not necessarily of the householder.)