{"id":1070,"date":"2015-11-03T10:28:55","date_gmt":"2015-11-03T10:28:55","guid":{"rendered":"http:\/\/demographicchartbook.com\/?page_id=1070"},"modified":"2015-11-04T06:03:09","modified_gmt":"2015-11-04T06:03:09","slug":"accuracy-of-the-data","status":"publish","type":"page","link":"https:\/\/demographicchartbook.com\/index.php\/about-the-demographic-chartbook\/accuracy-of-the-data\/","title":{"rendered":"Accuracy of the Data"},"content":{"rendered":"

General information on census data, including area classifications, definitions of topics, accuracy of the data, and collection and processing techniques, is provided in decennial census publications (and with census data sets on the Internet).\u00a0 The United States has been taken primarily on a de jure (usual place of residence) basis rather than on a de facto (location at the time of the census) basis.\u00a0 Estimates of census coverage and net under-enumeration have been prepared for the decennial census on a regular basis since 1940.\u00a0 While the estimated rates of net undercount have varied somewhat, they have generally shown higher rates of net undercount for males than for females, for young adults than for other age groups, and for minority groups than for the White (or White non-Hispanic) population.[12]<\/sup><\/p>\n

Since 1940, some data in the decennial census have been collected on a sample basis, and since 1960, this has been the case for data on most social and economic characteristics.\u00a0 The use of sample data (in decennial census publications and tabulations based on IPUMS) \u00a0is indicated in headnotes for the graphics.\u00a0 In general, estimates of sampling error are provided in decennial census publications that show sample data.<\/p>\n

Sample estimates may differ somewhat from the data that would have been obtained if information had been collected for the entire population.\u00a0 In addition to sampling error for data based on a sample, both 100-percent data and sample data are subject to nonsampling error.\u00a0 Nonsampling error may be introduced during any of the numerous operations used to collect and process data.\u00a0 Such errors may include the following: not enumerating every household or every person in the population, failing to obtain all required information from the respondents, obtaining incorrect or inconsistent information, and recording information incorrectly.\u00a0 In addition, errors can occur during the review of the enumerators\u2019 work, during clerical handling of the questionnaires, and during the processing of the questionnaires.<\/p>\n

The magnitude of sampling error is determined primarily by sample size and to a lesser degree by the sampling rate.\u00a0 Since the sample data shown in the graphics are for the United States, regions, states, and large cities (and not, for example, for small towns), the samples on which the sample data are based are sufficiently large that the resulting sampling errors are relatively small.\u00a0 As noted above, information on sampling error typically is provided in decennial census publications; however, the following very general guideline is offered, unless there is particular reason to question the comparability of data (e.g., due to changes in definitions).\u00a0 Changes (over time) and differences (for the same census year) of less than one or two percentage points (in the case of percentages) or of less than one or two percent (in the case of other measures, such as ratios, or numbers) do not merit emphasis.\u00a0 Such differences may not be statistically significant due to sampling error and\/or nonsampling error.\u00a0 In addition, such small changes may not be of substantive significance, even if they are of statistical significance.[13]<\/sup><\/p>\n

This general guideline does not apply to estimates based on sample data for net migration of the population born in the United States.\u00a0 In this case, estimates of in-migration and of out-migration are each subject to sampling error, and the resulting estimate of net migration, which may be a much smaller number, may have a large sampling error relative to the size of the estimate.<\/p>\n

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[12]<\/sup>For discussion and estimates of estimated net undercount, see U.S. Bureau of the Census, 1975 (Historical Statistics of the United States, Part 1, p. 1); Fay et al, 1988; Robinson et al, 1993; and U.S. Census Bureau, 2003.<\/p>\n

[13]<\/sup>For illustration, an example at the national level is provided using 1950 census data on children ever born to ever-married women.\u00a0 These data were based on a 3 and 1\/3 percent sample, much smaller than for most census sample data.\u00a0 For a weighted population of 1,000,000 (meaning about 33,000 sample cases), the standard error on an estimated percentage of 10 percent with zero children ever born\u00a0 is 0.2 percentage points, and the standard error on an estimated rate of 3.00 lifetime births per woman is 0.02 births (U.S. Bureau of the Census, 1955).\u00a0 There is about a 69-percent chance that the sample-based estimates would be within one standard error (and about a 95-percent chance within two standard errors) of what would have been obtained from a complete census.<\/p>\n","protected":false},"excerpt":{"rendered":"

General information on census data, including area classifications, definitions of topics, accuracy of the data, and collection and processing techniques, is provided in decennial census publications (and with census data sets on the Internet).\u00a0 The…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":690,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/pages\/1070"}],"collection":[{"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/comments?post=1070"}],"version-history":[{"count":2,"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/pages\/1070\/revisions"}],"predecessor-version":[{"id":1098,"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/pages\/1070\/revisions\/1098"}],"up":[{"embeddable":true,"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/pages\/690"}],"wp:attachment":[{"href":"https:\/\/demographicchartbook.com\/index.php\/wp-json\/wp\/v2\/media?parent=1070"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}