1990 Census Base Population Corrections, Adjustments, and Modifications Source: U.S. Bureau of the Census Population Estimates and Projections Program Extracted from: Report P25-1127 and updated to describe additional changes to the census base Internet Release date: July 1995 Updated: May 2000 The population estimates and projections presently produced by the Census Bureau incorporate corrections, adjustments, and modifications to the 1990 census enumerated resident population. The sections below provide brief descriptions of these changes. Footnotes are appended to provide additional detail or point the reader to other information sources. Census Population Corrections After the 1990 Census the Census Bureau processed changes to the enumerated population as processing errors linked to discrete census records were identified and corrected. These corrections first appeared in the 1994 estimates time series (1990-94) as an increase of 8,418 people in the 1990 United States population total to 248,718, 291. Additional corrections increased the corrected population, to 248,718,302. See footnote 1 for additional information on the correction process. Census Population Adjustments The national and sub-national population estimates and projections were not adjusted for net estimated under-enumeration in the 1990 census. However, population adjustments to the corrected 1990 Census base population that were consistent with the adjustment factors applied to the 1995 Test Census areas and the 1998 Dress Rehearsal sites were added to four states: California, Louisiana, New Jersey, and Wisconsin. The adjustments were statistically estimated to correct for over- and under- enumeration of household populations. No adjustments were made to group quarters population. The adjustments applied to these states produced a net increase of 72,623 people nationally, to 248,790,925 (see footnote 2 for additional detail). Age and Race Changes The Census Bureau's Estimates and Projections program modified the distribution of the national and subnational population by age and race. These modifications reconciled the definition of age and race with definitions used for data from other administrative sources, such as vital statistics. For AGE, the aim was to correct biases in census age tabulations that resulted from displacement of age reporting from the reference date (April 1) of the census. In 1990 census publications, age is based on respondents' direct reports of age at last birthday, with some editing for age misstatement. This definition proved inadequate for intercensal estimates, as many respondents reported their age (even if correctly) at the time of completion of the census form or interview by an enumerator, either of which could have occurred several months after the April 1 reference date. As a result, age was biased upward. Modification was based on a re-specification of age, for most individual respondents, according to their year of birth. Age was derived from year of birth by allocating date of birth to the first quarter and last three quarters of each year (using birth registration records), subtracting year of birth from 1990 for those born before April 1, and from 1989 for those born after April 1. The allocation was based on a historical series of registered births by month. Footnote 3 refers the reader to a source for additional information. For RACE, the goal of the modification was to conform to the definition of race specified in Office of Management and Budget (OMB) Directive 15. In the 1990 census, a substantial number of people (roughly 9.8 million) did not specify a racial group that could be classified as any of the White, Black, American Indian, Eskimo, Aleut, Asian, or Pacific Islander categories on the census form. A large majority of these persons were of Hispanic origin (based on their response to a separate, Hispanic origin question on the form), and many wrote in their Hispanic origin, or Hispanic origin type (for example, Mexican or Puerto Rican) as their race. Persons of unspecified race were allocated to one of the four tabulated racial groups (White, Black, American Indian, Asian and Pacific Islander) based on their response to the Hispanic origin question (see footnote 4). These four race categories conform with OMB Directive 15, and are more consistent with the race categories in other administrative sources (such as vital statistics) than are the original census tabulations. As was the case with age modification, the procedure was carried out through assignment of modified race on individual census records (see footnote 5). ------------------------------------------------------------------ Footnote 1. The count corrections reflected the reassignment of living quarters that were initially misallocated to the wrong geographic area, or corrections for over- or under- enumerated housing units and group quarters, as compared to individual 1990 Census enumeration records. A listing of governmental units affected by the Count Question Resolution process is in publication CPH-L-157, Corrected 1990 Census Population, Housing Unit, and Group Quarters Counts for Governmental Units, and is available from Population Division's Statistical Information Staff at (301) 457-2422 or pop@census.gov. Footnote 2. Household population adjustments from the 1995 Test Census sites were first applied to their respective counties and states, beginning with the 1997 estimates produced in calendar year 1998. The test areas and adjusted state populations were: State Adjusted Population (net increase) Test Area(s) New Jersey 7,747,750 (17,562) Paterson city (Passaic County) Louisiana 4,221,826 (1,662) Bienville, De Soto, Natchitoches, Jackson, Red River, and Winn Parishes California 29,785,857 (27,644) Oakland city (Alameda County) Household population adjustment from the 1998 Dress Rehearsal Sites were applied to their respective counties and states, beginning with the 1999 estimates produced in calendar year 2000. The sites and adjusted populations were: State Adjusted Population (net increase) Test Area(s) California 29,811,427 (25,570) Sacramento city (Sacramento County) Wisconsin 4,891,954 (185) Menominee County Footnote 3. For a more detailed description of the age modification procedures, see publication CPH-L-74, Age, Sex, and Hispanic Origin Information from the 1990 Census: A Comparison of Census Results with Results Where Age and Race have been Modified. For a comparison of this procedure with procedures used for the 1980 census, see Frederick W. Hollmann, U.S. Population Estimates, by Age, Sex, Race, and Hispanic Origin: 1980 to 1991, Current Population Reports, P25-1095. This publication is available from the Population Division's Statistical Information Staff at (301) 457-2422 or pop@census.gov. Footnote 4. "American Indian" refers to American Indian, Eskimo, and Aleut; "API" refers to Asian and Pacific Islander. Footnote 5. See footnote 3.