The Volume I State reports contain statistics on mobility status and 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, and statistics on mobility status and region of origin by age, sex, and color, 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 in1955 by region of residence in1960and the net gain or loss for each region through 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." Additional statistics on mobility for State economic areas are presented in report PC(2)-2B, Ability for States and State Economic Areas. Other 1960 Census reports on mobility are PC(2)-2A, State of Birth; PC(g)-2C, Mobility for Metropolitan Areas; and (2)-2D, Lifetime and Recent Migration. Additional statistics on the mobility of the population are in- eluded in a few other PC(2) and PC(3) reports.

The report PC(3)-1A, State Economic Areas, presents information on selected characteristics of persons for State economic areas with some characteristics shown separately for the urban, rural-nonfarm, and rural-farm population of the areas. These statistics were not tabulated for economic subregions, but corresponding information for the economic subregions can be obtained through the consolidation of the statistics for the State economic areas comprising the economic subregion using the list in appendix A.

Mobility data for 1950 are based on the based 1-year interval rather than the 5-year interval. The 1950 reports for States, Volume II, Characteristics of the Population, included statistics on residence in 1949 for the State, for standard metropolitan areas, urbanized areas, urban places with 10,000 inhabitants or more in 1950, and for counties. Data on mobility status were also 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 and Nonfarm Movers; and Part 4D, Population Mobility- Characteristics of Migrants. Some reports on other subjects in Volume IV, Special Reports, contained additional data on mobility cross-classified with the central subject of the report.

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

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 5-year interval (1935 to 1940) and hence from this standpoint is comparable to the 1960 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 for 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 have been published mostly in 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 304 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 these reports. Similar estimates of net migration can also be computed by age, sex, and colors and such estimates have been published by a number of agencies.²