On the basis of census returns on several items, including household relationship, marital status, age, and sex, the population in households is classified into several categories according to family status. Within households, persons who are family members are distinguished from those who are not family members. Persons in families are subdivided into those who are related to the household head (that is, persons in "primary families") and all others (persons in "secondary families"). Family members are further classified by relationship to the family head. Persons in households, who are not family members, are subdivided into those who are household heads (primary individuals) and those who are not household heads (secondary individuals). The complexity of this classification is a reflection of the variety of family living arrangements which characterize the population.

A household consists of all the persons who occupy a housing unit. A house, an apartment or other group of rooms, or a single room, is regarded as a housing unit when it is occupied or intended for occupancy as separate living quarters; that is, when the occupants do not live and eat with any other persons in the structure and there is either (1) direct access from the outside or through a common hall or (2) a kitchen or cooking equipment for the exclusive use of the occupants.

All persons who are not members of households are regarded as living in group quarters; that is, in living quarters for institutional inmates or for other groups containing five or more persons unrelated to the person in charge. Most of the persons in group quarters live in rooming houses, college dormitories, military barracks, or institutions. The present report excludes persons in group quarters, a very small number of whom may have had relatives present. In the 1960 Census, persons in group quarters were sampled on an individual basis, and no information on family relationship was obtained for them.

A family consists of two or more persons in the same household who are related to each other by blood, marriage, or adoption; all persons living together in one household who are related to each other are regarded as one family. For example, if the son of the head of the household and the son's wife are members of the household, they are treated as part of the head's family. A lodger and his wife who are not related to the head of the household, or a resident employee and his wife living in, are considered as a separate family, however. Thus, a household may contain more than one family. A household head living alone or with nonrelatives only is not regarded as a family. Some households, therefore, do not contain a family.

A "primary family" comprises the head of a household and all (one or more) other persons in the household related to the head. All other families are "secondary families"; these comprise groups of mutually related persons, such as lodgers or resident employees.

The delineation of families is based on the relationship reported, among persons who were usual residents of a housing unit at the time of the enumeration. For instance, college students were enumerated at the place where they lived while attending college, and persons living in military establishments were enumerated where they were stationed. Such persons were not included in the statistics for their parental homes, even though they may have intended to return home on their completion of college or period of service.

A subfamily is a married couple with or without children, or one parent with one or more own single children under 18 years old, living in a household and related to, but not including, the head of the household or his wife. The most common example' of a subfamily is a young married couple sharing the home of the husband's or wife's parents. Only those single sons and daughters under 18 years old of a subfamily head are regarded as children in the subfamily. Members of a subfamily are also members of a primary family. The number of subfamilies, therefore, is not included in the number of families.

A primary individual is a head of a household who is living entirely alone or with one or more persons none of whom is related to him.
Type of household, family, or subfamily
The classification of households, families, and subfamilies by type is based on the sex and marital status of the head. Households, families, and subfamilies with a head and his wife present are termed "husband-wife" households, families, or subfamilies. Households, families, and subfamilies with no spouse of head present are termed "other male head" or "female head," depending on the sex of the head.

A married couple is defined as a husband and his wife enumerated as members of the same household. The number of married couples is the sum of the number of husband-wife families and husband- wife subfamilies.

One person in each household is designated as the "head"; the number of heads of households is, therefore, equal to the number of households. The same principle applies to families and subfamilies. The head is generally the person so reported by the household respondent; however, in order to avoid establishing a separate category for the small number of families with the wife reported as the head, such families are edited to show the husband as the head.
Wife of household head, family head, or subfamily head
The number of women who are wives of heads in each category is the same as the number of husband- wife households, husband-wife families, or husband- wife subfamilies. The classification includes women in common-law marriages as well as women in formal marriages.

"Own" children in a household, family, or subfamily comprise the head's sons and daughters, including stepchildren and adopted children, living in the home. The count of own children under 18 years old is limited to single (never married) children; however, "own children under 25" and "own children of any age," as the terms are used here, include all children of the head regardless of marital status.

In a three-generation family, the determination as to whether there are any "own" children of the family head depends on which person in the family is identified as the head. If the family head belongs to the middle generation, his or her children are counted as "own" children of the family head. However, if a member of the oldest generation is reported as the family head, the members of the youngest generation are recorded as grandchildren rather than "own" children of the family head; in such a case the members of the youngest generation and their parents form a subfamily, in which the youngsters (under 18) are classified as "own" children of the subfamily head.

"Related" children, as the term is used in this report, include all family members under 18 except the family head and his wife, regardless of marital status. Thus, the category includes, in addition to "own children," all ever-married children under 18 of the family head and all grandchildren, nephews, cousins, etc., of the family head who were enumerated as members of the household. Related children other than own' children were identified in the coding operation only for those in primary families; such children, however, constitute well over 99 percent of all children in families.

Statistics on parents and grandchildren include parents and grandchildren of the wife of the head of a household or primary family as well as parents and grandchildren of the head. .

An other relative of the head is a person related to the head of the household by blood, marriage, or adoption, but not included specifically in another category.

A nonrelative of the head is any member of the household who is not related to the household head. This category includes lodgers (roomers and partners, relatives of such persons, and foster children) and resident employees (maids, hired farm hands, etc.).

Population reports for each census since 1850 contain figures on the number of households, but some of the earlier census figures are limited to the free population and have other limitations. After the 1900 Census had been taken, a few household characteristics for 1790 were tabulated for the free population in those areas with census records still in existence, and the results were reported in chapter VIII of A Century of Population Growth in the United States, 1790-1900, U.S. Government Printing Office, Washington, D.C., 1909. Beginning with 1890, more adequate household data in varying degrees of detail were published.

In 1947, the Bureau of the Census adopted a revised set of Household and family concepts. Statistics on "families" and "private households" in earlier reports are, in general, comparable with statistics on "households" in reports published in 1947 and subsequent years. In the 1960 and 1950 reports, the number of households is equal to the number of primary families plus the number of primary individuals. Primary individuals are persons who would have been classified as "one-person families" under the former terminology. The definition of families adopted in 1947 includes the small number of secondary families which would not have been classified as families under the old definition.

The definition of a household used in 1960 differs slightly from that used in the 1950 Census and in the 1940 Census. The change arises as a result of the shift from a dwelling unit to a housing unit as the basic unit of enumeration in the Census of Housing. According to the 1960 definition, a household consists of all the persons who occupy a housing unit, whereas in the 1950 and 1940 Censuses, a household consisted of all the persons who occupied a dwelling unit.

Table A. Population per Household, For the United States: 1890 to 1960
(Population includes persons not in households. Number of households for 1920, 1910, and 1890 includes quasi-households)

Area and census year	Households	Population per household
United States
1960	53,021,061	3.38
Conterminous United States
1960	52,810,747	3.38
1950	42,857,335	3.52
1940	34,948,666	3.77
1930	29,904,663	4.11
1920	24,351,676	4.34
1910	20,255,555	4.54
1900	15,963,965	4.76
1890	12,690,152	4.93

A dwelling unit was defined as: (1) A group of rooms occupied or intended for occupancy as separate quarters and having either separate cooking equipment or a separate entrance; or (2) a single room (a) if it had separate cooking equipment, (b) if it was located in a regular apartment house, or (c) if it constituted the only living quarters in the structure.

Housing units differ from dwelling units mainly in that separate living quarters consisting of one room with direct access but without cooking equipment always qualify as a housing unit in 1960 but qualified as a dwelling unit before 1960 only when located in a regular apartment house or when the room was the only living quarters in the structure.

The evidence so far available suggests that the change from the dwelling unit concept to the housing unit concept had relatively little effect on the number of households for the Nation as a whole and for large areas. Any effect which the change in concept may have can be expected to be greatest in statistics shown in other reports for some small areas, such as city blocks and census tracts. Living quarters classified as housing units in 1960 but which would not have been classified as dwelling units in the earlier censuses tend to be clustered in neighborhoods where many persons live alone in single rooms in hotels, rooming houses, and other light housekeeping quarters. For the 17 metropolitan areas shown separately in the report on the Components of Inventory Change survey of December 1959, the count of housing units for the combined 17 areas from the (April) 1960 Census is slightly higher than the count of dwelling units from the 1959 survey; this difference exists even after allowing for Sampling Variability of the 1959 estimate and the difference in dates of enumeration.

Furthermore, the estimate from the 1960 Census of the number of 1- and 2-room renter-occupied housing units in the 17 areas is higher than the estimate of dwelling units in the comparable category from the 1959 survey. ¹

The count of households in 1950, 1940, 1930, and 1900 excluded groups of persons living as members of quasi-households. However, the numbers for 1920, 1910, and 1850 to 1890 included quasi-households. A quasi- household was defined in 1950 as the occupants of s rooming house containing five or more persons not related to the head, or the occupants of certain other types of living quarters, such as dormitories, military barracks, and institutions. According to the 1940 definition, a rooming house was regarded as a quasi-household only when it included eleven or more persons not related to the head. The concept of quasi- household used in 1950 and 1940 is thus similar to the concept of group quarters used in 1960.

Except for the household concept, the other 1960 definitions relating to household and family composition are essentially the same as those previously used. However, the 1950 data on families include the small number in quasi-households, whereas, in 1960, statistics on families were compiled only for those in households.

Despite the similarity of definitions of household relationship, the national statistics for certain relatively small categories by relationship and family status appear to have been significantly affected through the change in the household definition. The change in household definition introduced in 1960 would theoretically tend to make the numbers of primary families and primary individuals enumerated in 1960 higher than the numbers that would have been obtained under earlier procedures, and to make the numbers of secondary families and secondary individuals lower. The evidence available indicates that, for the Nation as a whole, the number of husband-wife secondary families and the number of males classified as secondary individuals were lower in 1960 than they would have been under the earlier procedures. However, because these numbers are relatively small, even a substantial proportional reduction in them would not necessarily produce a significant increase in the national totals of the much more numerous primary families and primary individuals.

The number of households in the United States according to the 25-percent sample is virtually identical with the number according to the complete count, because the number in the sample was controlled to agree with that in the complete count (table B). This control did not extend, however, to the two types of households (primary families and primary individuals). Thus, the 25-percent sample as published underrepresented primary individuals by about 354,000, or 4 percent, and overrepresented husband-wife primary families by about 393,000, as compared with complete-count data. Moreover, the number of own children under 18 years of age was 1.3 percent larger in the 25-percent sample than in the complete count. Investigation of available data suggests that these differences arose primarily in the Sample Designation. The procedure for selecting the sample would have produced unbiased results if the design had been carried out according to instructions. The designation of the sample by the enumerator at the time he was canvassing was a low-cost procedure, which created some opportunity for undetected errors to occur and made control difficult.

The figures from the 4-percent sample tend to be in very close agreement with those from the 25-percent sample.

Table B. Comparison Of Complete-Count Data And Data From 25-Percent And 5-Percent Samples Of The 1960 Census Of Population And Data From The Current Population Survey, For The United States: 1960
(Numbers in thousands. Percent not shown where less than 0.1)

Subject	1960 Census							Current Population Survey
	Complete count	25-percent sample			5-percent sample			Total number	Deviation from 5-percent sample
		Total number	Deviation from complete count		Total number	Deviation from complete count
			Number	Percent		Number	Percent		Number	Percent
Households	53,021	53,024	3	…	53,019	-5	…	52,610	-409	-0.8
Primary families	44,670	45,027	357	0.8	45,048	21	…	44,856	-192	-0.4
Primary individuals	8,351	7,997	-354	-4.2	7,972	-25	-0.3	7,754	-218	-2.7
Families	(1)	45,128	(1)	(1)	45,149	21	…	45,062	-87	-0.2
Husband-wife families	(1)	39,641	(1)	(1)	39,657	16	…	39,335	-322	-0.8
Primary families	39,210	39,603	393	1.0	39,618	15	…	39,260	-358	-0.9
Subfamilies	(1)	1,424	(1)	(1)	1,428	4	0.3	1,511	83	5.8
Own children under 18 in families	259,582	60,347	765	1.3	59,877	-470	-0.8	59,833	-44	-0.1

¹ Not available.
²In primary families.

Comparisons of figures from the present report on the number of own or related, children under 18 years old of the family head with corresponding figures from certain other 1960 Census reports may be affected by the fact that the child's own sample inflation weight was invariably used in the present report, whereas the parent's sample inflation weight was used in other reports. Some of the tables in chapter D of Volume I, such as table l8l in the United States Summary, contain data on children under 18 that are weighted like those in table 6 of the present report, whereas other tables in chapter D, such as table 185 in the United States Summary, contain data on children based on the head's weight.

Table B includes comparisons of figures from the Current Population Survey (CPS) with those from the present report, which are based on the 1960 Census J-percent sample. Most of the key statistics in the CPS with regard to the numbers of households and families agree closely with those in the 5-percent sample. Thus, the numbers of families, subfamilies, primary individuals, and own children under 18 in the CPS and corresponding numbers in the 5-percent sample are within the limits of sampling error at the two-standard-error level (as measured from the CPS). The number of primary individuals in the CPS is 7 percent below the complete-count number in the census. The differences between census and CPS residence rules may be in part responsible for this result; in the census, students are counted in the community where they attend college (and where some of them maintain an apartment), but in the CPS, unmarried students are counted as residents of their parental homes.

In addition to persons of Negro and of mixed Negro and white descent, this classification includes persons of mixed Indian and Negro descent, unless the Indian ancestry predominates or unless the individual is regarded as an Indian in the community.

In addition to full-blooded Indians, persons of mixed white and Indian blood are included if the proportion of Indian blood is one-fourth or more, or if they are regarded as Indian in the community. Indians living in Indian territory or on reservations were not included in the population until 1890.

The category "other races" in table 1 includes all nonwhite races except Negro. In table 60, "other nonwhite races" includes all except Negro and American Indian.

Persons of mixed racial parentage are classified according to the race of the nonwhite parent, and mixtures of nonwhite races are classified according to the race of the father, with the special exceptions noted above.

This category comprises persons born in the United States, the Commonwealth of Puerto Rico, or a possession of the United States; persons born in a foreign country or at sea who have at least one native American parent; and persons whose place of birth was not reported and whose census report contained no contradictory information, such as an entry of a language spoken prior to coming to the United States.

This category includes all persons not classified as native.

This category -consists of native persons both of whose parents are also natives of the United States.

This category includes native persons one or both of whose parents are foreign born.

This category includes foreign-born persons and native persons of foreign or mixed parentage.

A housing unit is "owner occupied" if the owner or co-owner lives in the unit, even if it is mortgaged or not fully paid for. The head himself need not be the owner. All other occupied units are classified as "renter occupied," whether or not cash rent is paid. Examples of units for which no cash rent is paid include units occupied in exchange for services rendered, units owned by relatives and occupied without payment of rent, and units occupied by sharecroppers. Primary families are classified as "owner primary families" and "renter primary families" according to the tenure of the housing unit.

The number of household members includes all persons enumerated as usual residents of the housing unit whether related or not.

The number of persons per room was computed for each housing unit by dividing the total number of household members by the number of rooms in the unit. The number of rooms is the count of whole rooms used for living purposes, such as living rooms, dining rooms, bedrooms, kitchens, finished attic or basement rooms, recreation rooms, lodgers' rooms, and rooms used for offices by a person living in the unit. Not counted as rooms are bathrooms; halls, foyers, or vestibules; closets; alcoves; pantries; strip or pullman kitchens; laundry or furnace rooms; unfinished attics, basements, and other space used for storage.

In determining the number of units in the structure, the enumerator was instructed to count both occupied and vacant housing units but not to count business units or group quarters. A structure is defined as a separate building that either has open space on all four sides, or is separated from other structures by dividing walls that extend from ground to roof.

"Year built" refers to the date the original construction of the structure was completed, not to any later remodeling, addition, or conversion.

Living quarters are regarded as having direct access if the entrance is direct from the outside of the structure, or through a common hall, lobby, or vestibule used by the occupants of more than one unit. The hall, lobby, or vestibule must not be part of any unit, but must be clearly separate from all units in the structure. Living quarters do not have direct access when the only entrance to the room or rooms is through a room or hall which is part of another unit.

A kitchen is defined as a room used primarily for cooking and the preparation of meals. Cooking equipment is defined as (1) a range or stove, whether or not it is regularly used, or (2) other equipment such as a hotplate or electrical appliance if it is used for the regular preparation of meals. The category "with kitchen or cooking equipment" comprises units with facilities for exclusive use; the category "lacking kitchen or cooking equipment" comprises units with shared or no facilities. Equipment is for exclusive use if it is used only by the occupants of one unit.

The enumerator determined the condition of the housing unit by observation, on the basis of specified criteria related to the extent or degree of visible defects. Although detailed oral and written instructions and visual aids were provided, the application of the criteria involved some judgment on the part of the individual enumerator. The training program for enumerators was designed to minimize differences in judgment.

Sound housing is defined as that which has no defects, or only slight defects which are normally corrected during the course of regular maintenance. Deteriorating housing needs more repair than would be provided in the course of regular maintenance. Such housing has one or more defects of an intermediate nature that must be corrected if the unit is to continue to provide safe and adequate shelter. In some tables, "sound" and "deteriorating" are combined into one category, "not dilapidated."

Dilapidated housing does not provide safe and adequate shelter and in its present condition endangers the health, safety, or well-being of the occupants. Such housing has one or more critical defects, or has a combination of intermediate defects in sufficient number or extent to require considerable repair or rebuilding, or is of inadequate original construction. Critical defects result from continued neglect or lack of repair, or indicate serious damage to the structure.

A housing unit, with a flush toilet inside the structure and available to the occupants of the unit is classified according to whether it is for exclusive use or is shared with occupants of other units.

A housing unit has "hot piped water" if there is running water inside the structure and it is available to the occupants of the unit. A unit has piped hot water even though the hot water is not supplied continuously; for example, it may be supplied only at certain times of the day, week, or year.

A clothes washing machine owned by a member of the household was to be reported, whether it was located in the housing unit or elsewhere on the property. Machines used but not owned by members of the household, such as those provided by the management of an apartment building, were not to be reported. The number of households with a washer and a dryer (or a washer-dryer combination) are shown in some of the tables. Dryers used but not owned by members of the household, such as those provided by the management of an apartment building, were not to be reported.

A home food freezer is defined as an appliance, separate from the refrigerator, which freezes food and keeps food frozen. The freezer must be located in the housing unit or elsewhere on the property. Excluded is a freezer combined in the same cabinet with a refrigerator, even if it has a separate door.

A unit is classified as having a telephone if there is a telephone available to the occupants of the unit for receiving calls. The telephone may be located inside or outside the housing unit, and one telephone may serve the occupants of several units.

The count of automobiles available represents the number of passenger automobiles, including station wagons, owned or regularly used by any of the occupants of the housing unit. Passenger cars were to be counted if they were owned by a member of the household or if they were regularly used and ordinarily kept at home, such as some company cars. Not to be counted were taxis, pickups or larger trucks, and dismantled or dilapidated cars in an early stage of being junked. The statistics do not reflect, the number of automobiles privately owned or the number of households owning one or more automobiles.

Air conditioning is defined as the cooling of air by refrigerating apparatus. Excluded are evaporative coolers and fans or blowers which are not connected to a refrigerating apparatus. Separate statistics are shown in table 32 for primary families having air conditioners designed to cool one room and for those designed to cool more than one room (including central systems). A central system is an installation which air-conditions a number of rooms. In an apartment building, a central system usually provides air conditioning for all the apartments.

Television sets of all kinds located in the unit were to be included in the count-floor, table, built-in, portable, and combination with radio or phonograph. Sets in working order and sets being repaired were to be counted. A combination radio-television .set was' to be reported both as a television and as a radio set.

Value is the respondent's estimate of how much the property would sell for on the current market (April 1960). Value data are restricted to owner- occupied units having only one housing unit in the property and no business. Units in multiunit structures and trailers were excluded from the tabulations; and, in rural territory, units on farms and all units on places of 10 acres or more (whether farm or nonfarm) also were excluded.

Gross rent is shown as a percent of family income, for nonfarm primary families. Renter households not paying any rent for the housing unit are classified in the category "gross rent under 20 percent of income." Gross rent is based on the information reported for contract rent and the cost of utilities and fuel. Contract rent is the monthly rent agreed upon regardless of any furnishings, utilities, or services that may be included. The computed rent termed "gross rent" is the contract rent plus the average monthly cost of utilities (water, electricity, gas) and fuels such as wood, coal, and oil if these items are paid for by the renter. Thus, gross rent eliminates differentials which result from varying practices with respect to the inclusion of utilities and fuel as part of the rental payment. Bent data exclude rents for units in rural-farm territory.