Standard metropolitan areas.--Except in New England, a standard metropolitan area is a county or group of contiguous counties which contains at least one city of 50,000 inhabitants or more. In addition to the county, or counties, containing such a city, or cities, contiguous counties are included in a standard metropolitan area if according to certain criteria they are essentially metropolitan in character and socially and economically integrated with the central city. In New England, standard metropolitan areas have been defined on a town rather than county basis. Central cities.--The largest city in a standard metropolitan area is the principal central city. In 1950, any other city of 25,000 inhabitants or more within a standard metropolitan area was also designated as a central city. However, the maximum number of central cities permitted in any standard metropolitan area was three. In the case of the New YorkNortheastern New Jersey Standard Metropolitan Area, Jersey City and Newark were also considered central cities. The data for central cities for 1955 shown in this report relate to the cities as constituted in 1950, that is, annexations since April 1950 have not been taken into account. SOURCE AND RELIABILITY OF THE ESTIMATES Source of data.--The estimates presented in this report are based on data obtained in connection with the monthly population sample survey of the Bureau of the Census. This sample is spread over 230 sample areas comprising 453 counties and independent cities. A total of 24,000 to 26,000 dwelling units and other living quarters are designated for the sample at any time, and completed interviews are obtained each month from about 20,000 to 22,000 households. of the remainder, about 500 to 1,000 are households for which information should be obtained but is not, and the rest are vacant dwellings or those otherwise not to be enumerated for the survey. Reliability of the estimates.--Since the basis for the distribution by residence was the April 1955 sample survey, the estimates are subject to sampling variability. The following illustration indicates the order of magnitude of the sampling errors for some statistics in April 1955. An estimated 2,695,000 persons 35 to 44 years of age were living on rural farms. This number was 12.4 percent of the total number of persons living on rural farms. The relative sampling error is about 3.5 percent of the estimate of 2,695,000. The sampling error of the estimate of 12.4 percent is roughly one-half of one percentage point. The chances are about 68 out of 100 that the estimates from the sample differ from the results which would be obtained by a census by the sampling errors indicated for the above items. The chances are about 95 out of 100 that the differences would be less than twice the specified sampling errors and about 99 out of 100 that they would be less than 2 times the errors indicated. CIVILIAN POPULATION BY AGE AND SEX, FOR THE UNITED STATES, URBAN AND RURAL: APRIL 1955 AND 1950 (Figures for 1950 for age groups 55 to 69 years adjusted for apparent age bias in the nonwhite population; see text for explanation) tary school and kindergarten level than at the high school or college level. The number of children 5 to 13 years old enrolled in school (that is, the number who are usually in elementary school or kindergarten) increased by 28 percent in this 5-year span, whereas the number of persons 14 to 29 years old enrolled in school or college increased by only 13 percent. The age differences in rate of growth of the school population reflect mainly the past changes in numbers of births in the United States. FALL SCHOOL ENROLLMENT OF THE CIVILIAN NONINSTITUTIONAL POPULATION 5 TO 34 YEARS OLD, BY AGE, (Figures include children enrolled in kindergarten. Figures are rounded to the nearest thousand without being adjusted to group totals, which are independently rounded) |