A household consists of all the persons who occupy a housing unit (see definition of housing unit in section below on Living quarters). The population per household is obtained by dividing the population in households by the number of households. The population per household is not shown for nonwhite persons in tracts where most of the nonwhite persons live in the homes of white persons as nonrelatives; these persons perform domestic service work, live as lodgers while attending college, or have some other special living arrangement.

All persons who are not members of households are classified as living in group quarters. Most of the persons in group quarters live in rooming houses, college dormitories, military barracks, or institutions. Inmates of institutions are persons for whom care or custody is provided in such places as homes for delinquent or dependent children; homes and schools for the mentally or physically handicapped; places providing specialized medical care for persons with mental disorders, tuberculosis, or other chronic disease; nursing and domiciliary homes for the aged and dependent; prisons; and jails.

For persons in households, five categories of relationship to head of household are recognized in this report:

1.The head of the household is the member reported as the head by the household respondent. However, if a married woman living with her husband is reported as the head, her husband is classified as the head for the purpose of census tabulations.
2.The wife of a head of a household is a woman married to and living with a household head. This category includes women in common-law marriages as well as women in formal marriages.
3.The children under 18 of the household head are the heads sons and daughters under 18 years old and also his stepchildren and adopted children of this age group.
4.Other relative of head, in this report, includes all persons who are related to the head of the household by blood, marriage, or adoption except those in the categories wife of head and children under 18 of head.
5. A nonrelative of the head is any member of the household who is not related to the household head by blood, marriage, or adoption. Lodgers, partners, resident employees, wards, and foster children are included in this category.

Information on income for the calendar year 1959 was requested from all persons 14 years old and over in the sample. Total income is the sum of amounts reported separately for wage or salary income, self-employment income, and other income. Wage or salary income is defined as the total money earnings received for work performed as an employee. It represents the amount received before deductions for personal income taxes, Social Security, bond purchases, union dues, etc. Self-employment income is defined as net money income (gross receipts minus operating expenses) from a business, farm, or professional enterprise in which the person was engaged on his own account. Other income includes money income received from such sources as net rents, interest, dividends, Social Security benefits, pensions, veterans payments, unemployment insurance, and public assistance or other governmental payments, and periodic receipts from insurance policies or annuities. Not included as income are money received from the sale of property (unless the recipient was engaged in the business of selling such property), the value of income in kind, withdrawals of bank deposits, money borrowed, tax refunds, and gifts and- lump-sum inheritances or insurance payments. Although the time period covered by the income statistics is the calendar year 1959, the composition of families refers to the time of enumeration. For most of the families, however, the income reported was received by persons who were members of the family throughout 1959.

In order to obtain data on Spanish- and Mexican/Americans for areas of the United States where most of them live, white persons (and white heads of households) of Spanish surname were distinguished separately in five Southwestern States (Arizona, California, Colorado, New Mexico, and Texas). In all other States, Puerto Rican persons (and heads of households) were identified. Puerto Rican comprise persons born in Puerto Rico and persons of native parentage with at least one parent born in Puerto Rico.