Aggregate income is the sum of all incomes for a particular universe. Aggregate income is subject to rounding, which means that all cells in a matrix are rounded to the nearest hundred dollars. (For more information, see "Aggregate" under "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.

A family includes a householder and one or more other people living in the same household who are related to the householder by birth, marriage, or adoption. All people in a household who are related to the householder are regarded as members of his or her family. A family household may contain people not related to the householder, but those people are not included as part of the householder's family in census tabulations. Thus, the number of family households is equal to the number of families, but family households may include more members than do families. A household can contain only one family for purposes of census tabulations. Not all households contain families since a household may be comprised of a group of unrelated people or of one person living alone.

Families are classified by type as either a "married-couple family" or "other family" according to the presence of a spouse. "Other family" is further broken out according to the sex of the householder. The data on family type are based on answers to questions on sex and relationship that were asked on a 100-percent basis.

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.)