This report deals essentially with the streams, i.e., the number of persons living in a given State economic area (SEA) in 1955 but in another in 1960. Specifically, the statistics give the number of in- migrants into each SBA by SEA of residence in 1955, and the number of out-migrants from each SEA to the SEA of 1960 residence. Similar statistics are presented for economic subregions. In addition, the net gain or loss experienced by each economic subregion is also given. The net gain or loss through migration between State economic areas may be found in table 31 of the report PC(2)-2B.

The data on residence in 1955 were derived from the answers to the questions on the Household Questionnaire shown in the next column.

Residence on April 1, 1955, is 'the usual place of residence five years prior to enumeration. Residence in 1955 was used on conjunction with residence in1960to determine the mobility status of the population. The category "same house as in 1960" includes all persons 5 years old and over who were reported as living in the same house on the date of enumeration in 1960 and five years prior to enumeration. Included in the group are persons who had never moved during the five years, as well as those who had moved but by 1960 had returned to their 1955 residence. The category "different house in the United States" includes persons who, on April 1, 1955, lived in the United States in a different house from the one they occupied on April 1, 1960. These persons were subdivided into three groups according to their 1955 residence; viz., "different house, same county," "different county, same State," and "different State." The last category was further subdivided into contiguous and noncontiguous States'. States have been classified as contiguous if their boundaries touch at any point. For some distributions the different county category was subdivided into region, division, and State of 1955 residence. The category "abroad" includes those with residence in a foreign country or an outlying area of the United States in 1955« (In the coding of this item, persons who lived in Alaska or Hawaii in 1955 but in other States In 1960 were classified as living in a different State In 1955.³)



Persons 5 years old and over who had indicated they had moved into their present residence after April 1, 1955, but for whom, or for members of their families, sufficiently complete and consistent information concerning residence on April 1, 1955 was not collected, are included in the group "moved, place of residence in 1955 not reported." (Missing information was supplied if data were available for other members of the family.) Also included in the category "moved, place of residence in 1955 not reported" are persons who gave no indication as to their movement since April 1, 1955, hut who, on the basis of the final edited entry for year moved (for which all nonresponses were replaced by assigned entries), were classified as having moved into their present house since April 1, 1955.

Information on the quality of data on mobility status for 1960 is available from findings from the Content Evaluation Study (CES) of the 1960 Census, a postcensal study in which an intensive reinterview approach was used for a sample of census respondents. In the CES, measures of response error were developed with respect to selected items of information by comparing and reconciling the responses obtained in the reinterview with the corresponding census entries. Analysis of the CES data on mobility status indicates that, in general, the tendency is for the census to overestimate the more stable elements in the society and to underestimate the more mobile. The census showed fewer people living in a different State or abroad five years earlier than actually were living in a different State or abroad, and conversely, more people living in the same State, same county, and same house five years earlier than the resurvey revealed to be the case. One measure of the extent of the discrepancy is the distribution of interstate migrants in the resurvey by their classification in the census enumeration. Of those who were classified as interstate migrants in the CES and for whom mobility status was reported in the census, 85.6 percent were classified the same in the census, and the remainder were classified as having lived in the same State five years earlier (13.5 percent) or abroad (0.9 percent). The total number of interstate migrants enumerated by the census is 92.0 percent of the number estimated in the resurvey. Hence, the census also enumerated some persons as interstate migrants who, on the basis of the resurvey, actually were not interstate migrants. The two sets of comparisons taken together indicate that, in net terms, the census count is an underestimate of interstate migrants. The results of the 1960 Content Evaluation Study are not entirely comparable with those of the 1950 Post-Enumeration Survey. In considering comparative results, it should be noted that reported differences in quality may, in part, arise from improvement in procedures in the 1960 evaluation study, changes in accuracy between the 1960 and the 1950 Censuses, or both. For a more comprehensive report of the results of the evaluation studies, the reader is referred to Evaluation and ResearchProgram of the U.S. Censuses of Population and Housing: 1960, Series ER 60, No. 4, Accuracy of Data on Population Characteristics as Measured by Reinterviews, and to Bureau of the Census Technical Paper No. 4, The Post Enumeration Survey: 1950.

Similar questions on mobility were asked in the 1950 and 194-0 Censuses. However, the questions in the 1950 Census, as well as in annual supplements to the Current Population Survey, applied to residence one year earlier rather than five years earlier. In the 1950 reports, migrants reporting the State but not the county of residence in 1949 appear in the known categories of migration status and State of origin, whereas in this report such persons were all assigned to the category "moved, place of residence in 1955 not reported." This partial nonresponse group comprised 411,590 migrants in 1950; the corresponding figure for 1960 is not known. Although the questions in the 1940 Census covered a 5-year period, comparability with that census is reduced somewhat because of different definitions and categories of tabulation. In 1940, the population was classified in terms of four categories: Migrants, non-migrants, immigrants, and migration status not reported. The first group, "migrants," included those persons who in 1935 lived in a county (or quasi-county) different from the one in which, they were living in 1940. The second group, "nonmigrants," comprised those persons living in the same house in 1935 as in as well as persons living in a different house in the same county or quasi-county. The group classified as "immigrant" in 1940 is comparable to the group classified in 1960 as "abroad." The 1940 classification, "migration status not reported," included persons for whom information supplied was not sufficient for the assignment of a more specific category.

In accordance with Census practice dating back to 1790, each person enumerated in the 1960 Census was counted as an inhabitant of his usual place of residence or
usual place of abode, that is, the place where he lives and sleeps most of the time. This place is not necessarily the same as his legal residence, voting residence, or
domicile, although, in the vast majority of cases, the use of these different bases of classification would produce identical results.

The questions on place of residence in 1955 were supposed to refer to usual residence also. The respondent was not, however, furnished all the rules that the enumerator was instructed to use in determining the respondent's usual residence in 1960. Hence, in some cases, another type of residence may have been reported.

Except in New England, an SMSA is a county or group of contiguous counties which contains at least one city of 50,000 inhabitants or more, or "twin cities" with a
combined population of at least 50,000. In addition to the county, or counties, containing such a city or cities, contiguous counties are included in an SMSA if, according
to certain criteria, they are essentially metropolitan in character anti are socially and economically integrated, with the central city. In New England, SMSA's consist of
towns and cities, rather than counties.

These areas represent combinations of State economic areas. The 509 State economic areas are consolidated into a set of 121 areas which cut across State lines but which, as intended, preserve to a great extent the homogeneous character of the State economic areas. No changes were made in the boundaries of the 119 economic subregions of 1950 in conterminous United States. Two new subregions were established for the 1960 Census, one in Alaska and one in Hawaii. The SEA's comprising the economic subregions are shown in appendix A.