The Volume I State reports contain statistics on mobility status and the year moved into present house for States, by urban-rural residence, standard metropolitan statistical areas (SMSA's), urbanized areas, urban places of 10,000 or more, and counties. These reports also present statistics on mobility status and region of origin by age, color, and sex, for States and for cities of 250,000 or more.

The Volume I United States Summary report gives totals for the Nation and. its regions and geographic divisions and shows region of residence in 1955 by region of residence in 1960 and the net gain or loss for each region by interregional migration.

Statistics on place of residence in 1955 are presented in Census Tracts. Series PHC(1). Movers living in each census tract are classified by 1955 residence as follows: (1) Central city of this SMSA, (2) other part of this SMSA, and (3) outside this SMSA. The last category is further subdivided into "North and West" and "South." Other 1960 Census reports on mobility are PC(2) -2A, State of Birth; PC(2)-2B, Mobility for States and State Economic Areas; and PC(2)-2D, Lifetime and Recent Migration. The report, PC(3)-1D, Standard Metropolitan Statistical Areas, includes some data on mobility. Additional statistics on the mobility of the population are included in a few other PC(2) and PC(3) reports.

Mobility data for 1950 are based on a one-year interval, 19U9-1950, rather than a five-year interval. The 1950 reports for States, Volume II, Characteristics of the Population, included statistics on residence in 19^9 for the State, for standard metropolitan areas, urbanized areas, urban places with 10,000 inhabitants or more in 1950, and counties. Data on mobility status were presented for census tracts in Volume III of the 1950 reports. Volume IV of the 1950 Census included four special reports on mobility, namely: Part 4A, State of Birth; Part 4B, Population Mobility-States and State Economic Areas; Part 4C, Population Mobility-Farm-Nonfarm Movers; and Part 4D, Population Mobility-Characteristics of Migrants. Additional data on mobility were presented in Volume IV, Special Reports, with other subjects.

The 1940 Census, in which for the first time data were obtained on the mobility of the population during a fixed period of time, used a five-year interval (1935 to 1940) and hence from this standpoint is comparable to the1960 Census. Although the population schedule called for a report on all changes of usual residence, in the main tabulations, persons moving from one house to another within the same county, or quasi-county,¹ were not distinguished from those in the same house at both dates. All these persons, as well as children under 5 years old, were described as "nonmigrants" in the 1940 reports. Data were presented for the United States, regions, geographic divisions, States, urban and rural residence, and individual cities of 100,000 inhabitants or more. Statistics were published in four special reports entitled Color and Sex of Migrants, Age of Migrants, Economic Characteristics of Migrants, and Social Characteristics of Migrants. Additional statistics on migration were contained in some of the special reports on other subjects.

Sample data on mobility during the preceding year have been collected annually since 1948 in the Current Population Survey and published mostly in the Current Population Reports, Series P-20. Earlier surveys at irregular intervals covered other periods back to 1940.

Estimates of net migration including net immigration from abroad by States and counties have been computed for the decade 1950 to 1960. The State estimates are published in Current Population Reports, Series P-25, No. 247, and the county estimates in Series P-23, No. 7. The methods of computing net migration and net civilian migration by the so-called "residual method" are explained in both reports. Similar estimates of net migration can also be computed by age, color, and sex; and such estimates have been published by a number of agencies.

¹ A quasi-county was defined as a city of 100,000 or more or the balance of the county.