The statistics on State of birth are of value mainly for the information they provide on the historic movements of the native population from one State to another within the United States from the time of birth to the date of the census. Extreme care should be exercised in the use of the statistics as representing or measuring migration, however, since in this connection they indicate only the net result of migration during the differing periods of the life of the persons enumerated.

The census figures on State of birth reflect the migration of only those persons who have moved from one State to another and are, on the date of the census, living in States other than those in which they were born. The statistics, therefore, afford no indication of the amount of migration within a given State from rural to urban communities or from one locality to another; nor do they take any account of intermediate moves between the time of a person's birth and the time of the census.

The statistics thus do not indicate the total number a persons who have moved from the State in which they were born to other States, or to any specific State, during any given period of time. Some of those who had gone from one State to another have since died others have returned to the State in which they were born, and others have gone to still other States, or to places outside the United States.

The net gain or loss through interregional movement (tables 5 and 16) interdivisional movement (tables 6, 7, 8, and 17), or interstate movement (tables 11 to 14) represents the difference in the census data between the total number of surviving native persons who had moved out of the specified area since they were born and the total number of surviving native persons who had moved into the specified area since they were born. Some of these persons are the survivors of groups who departed from or arrived in the area half a century or more before the census date. The figures, therefore, do not represent migration in the sense of the number of persons coming or going during the previous census decade or during any other specific period of time. The "change in net gain or loss as compared with the previous census," as shown in the final column of table 7, represents the algebraic difference between the net gains or losses at the beginning and end of the decade. Even this figure, however, does not represent exactly the difference between the number of native migrants out of the region and the number of native migrants into the region, since it is affected also by differences in mortality and by the movement of the native population between the area in question and foreign countries.

Although it is not possible to estimate migration during a given decade from statistics on State of birth, it is possible to make such estimates from other census statistics. Specifically, net migration for a given Stats, or other area, for a given inter-censal decade can be estimated relative to all other areas combined. Such estimates may also be made by age, sex, race, and nativity. Very briefly, the procedure consists of starting with the population in a given State at a particular census, allowing for mortality during the decade, and subtracting the numbers of estimated survivors from the corresponding population enumerated in the State at the next census. The Census Bureau has published estimates by this so-called "residual method" by States for the period 1950 to 1960 in Current Population Reports, Series P-25. (See for example Nos. 227 and 247.) Estimates for counties, State economic areas, etc., are published in Current Population Reports. Series P-23, No. 7.

The present report is the second to present State- of-birth data cross-classified by fairly detailed age distribution. These data give somewhat more information on the time of migration than the data shown for earlier censuses. With the use of appropriate mortality rates, one can compute, for example, from the number of persons 20 to 29 years old living in California in 1950 but born in another State, the number expected in the same category 30 to 39 years old in 1960 had there been no further in-migration during the decade. A comparison of the expected and observed numbers for 1960 will indicate the approximate in- migration to California in this age cohort during the decade, If in-migrants during the decade are defined as those who came into the State during the decade and were still living there at the end of the decade. The chief source of error in this approximation is the departures of former In-migrants. Similarly, fairly good estimates can be made of the total out-migrants from a given State to all other States and of the net migration. Using the figures on the number born and still living in the same State at successive censuses, one can also identify the age groups in which there has been further net out-migration during the decade and those In which there has been net return migration.

State of birth statistics by age at successive censuses yield much less accurate estimates, however, of particular streams of migration during the decade. Consider, for example, the 1950-1960 migrants from New England to California. The additional complication here is that one does not know whether the decennial increment in the New England-born represents persons who left New England during the decade or whether it represents persons who left New England prior to 1950 and were living in a third area in 1950 - Iowa, for example. The only exception is the case of the children under 10 years old at the time of the latest census, who obviously left their birthplace during the most recent decade.

For persons who are living in a different State from the State of their birth, the data Indicate whether the interstate move occurred between contiguous or noncontiguous States. States have been classified as contiguous if their boundaries touch at any point.<sup>1

1</sup>The following is a list of the contiguous States for each State:

Alabama	Fla., Ga., Miss., Term.
Alaska	None
Arizona	Calif., Colo., Nev., N. Mex., Utah
Arkansas	La., Miss., Mo., Okla., Tenn., Texas
California	Ariz., Nev., Oreg.
Colorado	Ariz., Kans., Nebr., N. Mex., Okla., Utah, Wyo.
Connecticut	Mass., N.Y., R.I.
Delaware	Md., N.J., Pa.
Dist. of Col.	Md., Va.
Florida	Ala., Ga.
Georgia	Ala., Fla., N.C., S.C., Tenn.
Hawaii	None
Idaho	Mont., Nev., Oreg., Utah, Wash., Wyo.
Illinois	Ind., Iowa, Ky., Mo., Wis.
Indiana	Ill., Ky., Mich., Ohio
Iowa	Ill., Minn., Mo., Nebr., S. Dak., Wis.
Kansas	Colo., Mo., Nebr., Okla.
Kentucky	Ill., Ind., Mo., Ohio, Tenn., Va., W.Va.
Louisiana	Ark., Miss,, Texas
Maine	N.H.
Maryland	Del., D.C., Pa., Va., W.Va.
Massachusetts	Conn., N.H., N.Y., R.I., Vt.
Michigan	Ind., Ohio, Wis.
Minnesota	Iowa, N. Dak., S. Dak., Wis.
Mississippi	Ala., Ark., La., Tenn.
Missouri	Ark., Ill., Iowa, Kans., Ky.,Nebr., Okla., Tenn.
Montana	Idaho, N. Dak., S. Dak., Vyo.
Nebraska	Colo., Iowa, Kans., Mo., S. Dak., Wyo.
Nevada	Ariz., Calif., Idaho, Oreg., Utah
New Hampshire	Maine, Mass., Vt.
New Jersey	Del., N.Y., Pa.
New Mexico	Ariz., Colo., Okla., Texas, Utah
New York	Conn., Mass., N.J., Pa., Vt.
North Carolina	Ga., S.C., Tenn., Va.
North Dakota	Minn., Mont., S, Dak.
Ohio	Ind., Ky., Mich., Pa., W.Va.
Oklahoma	Ark., Colo., Kans., Mo., N. Mex., Texas
Oregon	Calif., Idaho, Nev., Wash.
Pennsylvania	Del., Md., N.J., N.Y., Ohio, W.Va.
Rhode Island	Conn., Mass.
South Carolina	Ga., N.C.
South Dakota	Iowa, Minn., Mont., Nebr., N. Dak., Wyo.
Tennessee	Ala., Ark., Ga., Ky., Miss., Mo., N.C., Va.
Texas	Ark., La., N. Mex., Okla.
Utah	Ariz., Colo., Idaho, Nev., N. Mex., Wyo.
Vermont	Mass., N.H., N.Y.
Virginia	D.C., Ky., Md., N.C., Tenn., W.Va.
Washington	Idaho, Oreg.
West Virginia	Ky., Md., Ohio, Pa., Va.
Wisconsin	Ill., Iowa, Mich., Minn.
Wyoming	Colo., Idaho, Mont., Nebr., S. Dak., Utah

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.

The category "born in outlying areas" includes persons born in the Commonwealth of Puerto Rico and other areas of United States sovereignty or jurisdiction. The areas included vary from census to census. Persons born in Alaska and Hawaii, for example, were included in this category prior to 1960 and are so shown where the 1960 data relate to conterminous United States. Persons born in the Philippine Islands were included in this, category from the Census of 1900 through that of 1940.

The definition of the category "born abroad or at sea of American parents" in the 1960 Census differs from that used in previous years. Prior to 1960, persons born outside the United States, the Commonwealth of Puerto Rico, and other areas of sovereignty and jurisdiction were classified as native if their parents were citizens of the United States. In 1960, there was no general inquiry on citizenship, and thus it was not possible to identify as native the children born abroad to naturalized American citizens.

Nonetheless, there was a substantial increase in the number of persons counted in this category, from about 96,000 in 1950 to about 400,000 in 1960. A part of this increase reflects, of course, the increase in the number of members of the Armed Forces and civilian Federal employees and their respective families living abroad. A total of 332,000 births occurring abroad to these American citizens were voluntarily reported by their parents in the decade 1950 to 1960. This number is reflected in about 140,000 "native" children under 10 years old who were reported in the 1960 Census as having been born abroad. Since many of those born abroad are still living there, the number counted in the 1960 Census would be expected to be lower than
332,000.

This category includes all persons not classified as native.