General Note: Average annual percent changes for items in this table were computed using the compound interest rate formula. Absolute values or values with less rounding than appear here were used in the computations.

The source table cited for each item generally provides more complete information and notations concerning the item. In a number of instances, figures in this table represent revisions and supersede figures shown elsewhere in this volume. Standard Notes: - Represents zero. na Not available. ns Percent change not relevant or significant. x Not applicable. z Less than 0.05 percent.

Where na occurs in 1972 column only, percent change calculated refers to 1970-71 period.

2 As of July 1, except as noted. Resident population excludes Armed Forces abroad, except as noted. 1960 and 1970 data as of April 1. 1960-70.

Excludes Armed Forces living in barracks in U.S., therefore will not add to total resident population.

As of March.

7 Includes Armed Forces.

1967.

⚫ 1967-70.

10

Not strictly comparable with earlier years.

I 1961.

12 1961-65.

19 1964.

Section 1

Population

This section presents statistics on the growth, distribution, and characteristics of the population of the United States. The principal source of these data is the Bureau of the Census, which conducts a decennial census of the populatiɔn and a monthly current population survey and also prepares periodic population estimates. For a list of publications, see the Guide to Sources in Appendix III of this book.

Decennial censuses.-The Constitution provides for a census of population within every 10-year period, primarily to establish a basis for apportionment of Members of the House of Representatives among the States. For over a century after the first census in 1790, the census organization was a temporary one. In 1902, the Bureau of the Census was established as a permanent Federal agency, responsible for enumerating the population and also for compiling statistics on other subjects and at other times.

In population censuses, each person is counted as an inhabitant of his usual place of residence. While this place is not necessarily his legal residence, voting residence, or domicile, the use of these different bases of classification would usually produce substantially the same statistics.

In recent censuses, some data were obtained from representative samples of the population rather than from a complete count, as follows: 5 percent in 1940, 20 percent in 1950, 25 percent in 1960, and 5, 15, and 20 percent in 1970. Exact agreement is not to be expected among the various samples, nor between them and the complete count, but sample data may be used with confidence where large numbers are involved and assumed to indicate patterns and relationships where small numbers are involved.

Estimates based on evaluation studies of the 1970 census results indicate a total net underenumeration of about 5.3 million persons, compared with 5.1 million in 1960. Among the persons who were not counted in 1970, about 3.4 million were white and about 1.9 million were Negro. The overall rate of net underenumeration in 1970 was about 2.5 percent, compared with 2.7 percent in 1960 and 3.3 percent in 1950. Data from the 1950, 1960, and 1970 censuses have not been adjusted for the estimated underenumeration.

Current Population Survey.-This is a monthly nationwide survey of a scientifically selected sample representing the noninstitutional civilian population. The sample is located in 449 areas comprising 863 counties and independent cities with coverage in every State and the District of Columbia. About 58,500 housing units and other quarters are designated for the sample at any time, of which about 50,000 (containing 105,000 persons 16 years old and over) are occupied by households eligible for interview; of these, in turn, about 4 to 6 percent are, for various reasons, unavailable for interview. See also text, section 8, Labor Force, Employment, and Earnings.

Population estimates and projections.-National estimates are derived by use of decennial census data as benchmarks and of data available from various agencies as follows: Births and deaths (Public Health Service); immigrants (Immigration and Naturalization Service); the Armed Forces (Department of Defense); net movement between Puerto Rico and the U.S. mainland (Puerto Rico Planning Board); and Federal employees abroad (Civil Service Commission and Department of Defense). State estimates are based on similar data and also on a variety of data series, including school statistics from State departments of education and parochial school systems. National population projections indicate the approximate future level and characteristics of the population under given assumptions as to future fertility, mortality,

and net immigration. The method used to develop the projections involved preparation of projections of each of the components of population change-births, deaths, and net immigration—and the combination of these with July 1 estimates of the current population. Projections for States and metropolitan areas incorporate further assumptions about population redistribution through interarea migration.

Current estimates and projections are consistent with official census figures and are not adjusted for estimated census underenumeration. For details on methodology, see the source cited below individual tables.

Standard Metropolitan Statistical Areas (SMSA).—The entire territory of the United States has been classified by the Office of Management and Budget as (a) metropolitan, or "inside SMSA's,” and (b) nonmetropolitan, or "outside SMSA's." For descriptive details, see the introductory text to section 33 of this book. A listing of area titles and components of each SMSA is given at the end of section 33.

Urban and rural areas.-According to the 1970 census definition, the urban population comprises all persons in (a) places of 2,500 inhabitants or more incorporated as cities, villages, boroughs (except Alaska), and towns (except in New England, New York, and Wisconsin), but excluding persons living in the rural portions of extended cities; (b) unincorporated places of 2,500 inhabitants or more; and (c) other territory, incorporated or unincorporated, included in urbanized areas. Some urbanized areas contain one or more incorporated places which are designated as "extended cities" because they have one or more large portions (normally at the city boundary) with relatively low population density. These portions are classified as rural.

In 1960 (but not in 1970), certain towns in New England, townships in New Jersey and Pennsylvania, and counties elsewhere were also designated as urban. Substantially the same definition was used in the 1950 census as in the 1970 census except for the introduction of the concept of "extended cities." In censuses prior to 1950, the urban population comprised all persons living in incorporated places of 2,500 inhabitants or more and areas (usually minor civil divisions) classified as urban under somewhat different rules relating to population size and density. In all definitions, the population not classified as urban constitutes the rural population.

Changes in the size of the urban population from one census to another are affected by 2 components: (a) Growth in areas classified as urban at the beginning of the decade; and (b) reclassification of rural territory as urban and urban territory as rural. Between censuses, it is possible only to obtain measures of the first component from the Current Population Survey (see p. 1). Measures of the second are too costly. Since about 40 percent of the urban population growth between 1960 and 1970 was attributable to expansion of urban territory, data on the urban population from the Survey may be misleading. Consequently, publication of data on urban-rural residence from the Current Population Survey has been discontinued.

Farm and nonfarm residence.-The rural population is divided into "rural-farm," comprising persons living on farms, and "rural-nonfarm," comprising the remainder. According to the 1960 and 1970 census definitions, the farm population consists of persons living in rural areas on places of less than 10 acres yielding agricultural products which sold for $250 or more in the previous year, or on places of 10 acres or more yielding agricultural products which sold for $50 or more in the previous year.

Race. The population is divided into three major groups on the basis of race: White, Negro, and other. The 1960 and 1970 censuses obtained the information on race principally through self-enumeration; thus, the data represent essentially selfclassification by people according to the race with which they identify themselves. Persons of Mexican or Puerto Rican birth or ancestry who did not identify themselves as of a race other than white were classified as white. In 1970, the father's race was used for persons of mixed parentage who were in doubt as to their classification. In 1960, persons who reported mixed parentage of white and any other race were classified

according to the other race; mixtures of races other than white were classified according to the father's race.

Mobility status.-Classification of the population by mobility status is based on comparison of an individual's place of residence at the survey or census date with that of a specified earlier date. Mobile persons or movers includes all persons living in different houses in the United States at the beginning and at the end of the period. According to their new location, they may be "same county movers" or "different county movers, or migrants." Migrants in turn are classified according to whether they moved within the same State or into a different State. Nonmobile persons or nonmovers includes all persons living in the same house in the United States at the beginning and end of the period. Persons abroad includes all persons living outside the United States at the beginning of the period.

Nativity. The category "Native" comprises persons born in the United States, the Commonwealth of Puerto Rico, an outlying area of the United States, or at sea. It also includes persons born in a foreign country who have at least one parent born in the United States. Persons not having any of the foregoing qualifications are classified as "foreign born."

Ethnic Origin.-"Ethnic origin" is determined on the basis of a question asking for self-identification of the person's origin or descent and is, therefore, a report on what persons perceive their origin to be. A question on ethnic origin was included in the 1971 and 1972 Current Population Surveys. The answers to this question produce results somewhat different from those based on inferences from such characteristics as place of birth, country of origin, language spoken in the home, or surname.

Household.—A "household" comprises all persons who occupy a "housing unit," that is, a house, an apartment or other group of rooms, or a room that constitutes "separate living quarters." A household includes the related family members and all the unrelated persons, if any, such as lodgers, foster children, wards, or employees who share the housing unit. A person living alone or a group of unrelated persons sharing the same housing unit as partners is also counted as a household. See text, section 27, Construction and Housing, for definition of "housing unit."

Group quarters are living arrangements for persons who do not live in housing units. Examples of group quarters are: A rooming house, an institution, a college dormitory, or a military barracks.

Family. The term "family" refers to a group of two or more persons related by blood, marriage, or adoption and residing together in a household. A primary family consists of the head of a household and all other persons in the household related to the head. A secondary family comprises two or more persons such as guests, lodgers, or resident employees and their relatives, living in a household and related to each other. Subfamily. A "subfamily" is a married couple with or without children, or one parent with one or more unmarried children under 18 years old, living in a household and related to, but not including, the head of the household or his wife. Members of a subfamily are also members of the primary family with whom they live. The number of subfamilies, therefore, is not included in the number of families.

Married couple.-A "married couple" is defined as a husband and his wife living together in the same household, with or without children and other relatives.

Unrelated individuals.—“Unrelated individuals" refers to persons (other than inmates of institutions) who are not living with any relatives. A primary individual is a household head living alone or with nonrelatives only. A secondary individual in a household is a person such as a guest, lodger, or resident employee who is not related to any other person in the household. Persons in group quarters, except inmates of institutions, are classified as secondary individuals.

Historical statistics.-Tabular headnotes provide cross-references, where applicable, to Historical Statistics of the United States, Colonial Times to 1957. See preface.