Documentation for Bridged-Race Vintage 2008
(July 1, 2000 - July 1, 2008)
Postcensal Population Estimates
for Calculating Vital Rates
On September 2, 2009, the National Center for Health Statistics released the Bridged-race Vintage 2008 postcensal population file.
The Vintage 2008 bridged-race postcensal population estimates files contain estimates of the resident population of the United States as of July 1, 2000 to July 1, 2008, by county, single-year of age (0, 1, 2,..., 85 years and over), bridged-race category (White, Black or African American, American Indian or Alaska Native, Asian or Pacific Islander), Hispanic origin (not Hispanic or Latino, Hispanic or Latino), and sex (1). The estimates on this file are based on Census 2000 and result from bridging the Vintage 2008 postcensal estimates with 31 race groups (the 31 race groups used in Census 2000 in accordance with the 1997 Office of Management and Budget (OMB) standards for the collection of data on race and ethnicity) to the four race categories specified under the 1977 OMB standards (2,3).
Source of the Estimates
The Vintage 2008 bridged-race postcensal estimates were produced by the Population Estimates Program of the U.S. Census Bureau in collaboration with the National Center for Health Statistics (NCHS). This file was released by the Census Bureau on May 14, 2009 and by NCHS on September 2, 2009.
Changes in Estimates Methodology Implemented for Vintage 2008
The Vintage 2008 postcensal population estimates reflect three major improvements in the estimates methodology (4,5). Improvements include changes in
- the estimation of net international migration,
- the incorporation of accepted challenges and special censuses into the national population estimates, and
- the imputation of the race and Hispanic origin for births.
In an effort to produce the most accurate and effective estimates, the Census Bureau retained adjustments developed for the Vintage 2006 and Vintage 2007 estimates in the Vintage 2008 estimation procedures. These adjustments accommodate geographic shifts in the populations of Alabama, Louisiana, Mississippi and Texas resulting from Hurricanes Katrina and Rita in 2005 (7,8,9).
Geographic Codes in the Bridged-Race Population Files
The Vintage 2008 files have population estimates for 3,142 counties and county equivalents. The Federal Information Processing System (FIPS) codes on the Vintage 2008 files differ slightly from those on earlier vintages: two new FIPS codes are included on the files (Skagway Municipality and Hoonah-Angoon Census Area) and one FIPS code is excluded (Skagway-Hoonah-Angoon Census Area). The table below summarizes differences in FIPS codes across the various bridged-race population files; for the most part, FIPS codes on the files are the same. Vintage 2002, Vintage 2005, Vintage 2006, and Vintage 2007 have estimates for 3,141 counties and county equivalents and the FIPS codes on these four vintages are consistent with each other. The Vintage 2003 and Vintage 2004 files have estimates for 3,140 counties and county equivalents and the FIPS codes on these two vintages are consistent with each other (unlike the other postcensal vintages, they do not have population estimates for Broomfield County, Colorado). The 1990-1999 intercensal files and the April 1, 2000 files have estimates for 3,141 counties and county equivalents; these files do not have estimates for Broomfield, CO but unlike later files do have estimates for Clifton Forge, VA.
| Counties and county equivalents that do not appear on all of the bridged-race population files: 1990-2008 | ||||||
|---|---|---|---|---|---|---|
| County or County Equivalent | ||||||
| Years | Number of Counties | Skagway Municipality, AK | Hoonah-Angoon Census Area, AK | Skagway-Hoonah-Angoon Census Area, AK | Broomfield County, CO | Clifton Forge County, VA |
| Intercensal estimates | ||||||
| 1990 - 1999 | 3,141 | --*-- | --*-- | X | --*-- | X |
| Census counts 2000 | ||||||
| April 1, 2000 | 3,141 | --*-- | --*-- | X | --*-- | X |
| Postcensal estimates | ||||||
| Vintage 2001 | None, only national estimates. | |||||
| Vintage 2002 | 3,141 | --*-- | --*-- | X | X | --*-- |
| Vintage 2003 | 3,140 | --*-- | --*-- | X | --*-- | --*-- |
| Vintage 2004 | 3,140 | --*-- | --*-- | X | --*-- | --*-- |
| Vintage 2005 | 3,141 | --*-- | --*-- | X | X | --*-- |
| Vintage 2006 | 3,141 | --*-- | --*-- | X | X | --*-- |
| Vintage 2007 | 3,141 | --*-- | --*-- | X | X | --*-- |
| Vintage 2008 | 3,142 | X | X | --*-- | X | --*-- |
| --*-- County or county equivalent is not on the file. | ||||||
| X County or county equivalent is on the file. | ||||||
Specific details:
-
Broomfield County, Colorado (FIPS code=08014) was created effective November 15, 2001 from parts of four Colorado counties: Adams, Boulder, Jefferson, and Weld. There are estimates for this county on some, but not all, of the bridged-race files. Note that data for Broomfield County do not appear on NCHS birth or mortality files until data year 2003.
Clifton Forge County, Virginia (FIPS code = 51560). On July 1, 2001, Clifton Forge city, Virginia, formerly an independent city, merged with Alleghany county (FIPS code=51005). There are no estimates for this county on the bridged-race postcensal population files. Note that data for Clifton Forge city appear on NCHS birth and mortality files prior to data year 2003; beginning with the 2003 data year, no data for Clifton Forge city appear on the birth and death files.
Skagway Municipality, Alaska (FIPS code = 02230). Skagway Municipality was created from part of the former Skagway-Hoonah-Angoon Census Area (FIPS code = 02232) effective June 20, 2007; boundaries are identical to the Skagway census subarea; population: 862. The remainder of the former Skagway-Hoonah-Angoon Census Area was established as the new Hoonah-Angoon Census Area (02105). This county equivalent appears only on the Vintage 2008 files. Note that no data for Skagway Municipality appear on NCHS birth and mortality files.
Hoonah-Angoon Census Area, Alaska (FIPS code = 02105). The Hoonah-Angoon Census Area was created from the remainder of the former Skagway-Hoonah-Angoon Census Area (FIPS code = 02232) when Skagway Municipality (FIPS code = 02230) was created effective June 20, 2007; population: 2,574. This county equivalent appears only on the Vintage 2008 files. Note that no data for Hoonah-Angoon Census Area appear on NCHS birth and mortality files.
Skagway-Hoonah-Angoon Census Area, Alaska (FIPS code = 02232). Effective June 20, 2007, Skagway-Hoonah-Angoon Census area was split to create Skagway Municipality (FIPS = 02230) and Hoonah-Angoon Census Area (FIPS code = 02105). This county equivalent appears on the bridged-race files prior to Vintage 2008 (except for Vintage 2001 for which no county-level data are available). Note that data for Skagway-Hoonah-Angoon Census Area appear on NCHS birth and mortality files for years 1994 - the present.
Race Bridging Background
What is race bridging? Race bridging refers to making data collected using one set of race categories consistent with data collected using a different set of race categories, to permit estimation and comparison of race-specific statistics at a point in time or over time. More specifically, race bridging is a method used to make multiple-race and single-race data collection systems sufficiently comparable to permit estimation and analysis of race-specific statistics.
OMB's 1977 and 1997 standards on race and ethnicity: In 1997, OMB issued "Revisions to the Standards for the Classification of Federal Data on Race and Ethnicity," which supersedes the 1977 "Statistical Policy Directive 15, Race and Ethnic Standards for Federal Statistics and Administrative Reporting" (2,3). Both documents specify rules for the collection, tabulation, and presentation of race and ethnicity data within the Federal statistical system. The race categories specified in both standards represent a social-political construct and are not anthropologically or biologically based. The revised standards increased the minimum number of race categories to be used by Federal agencies from four (White, Black, American Indian or Alaska Native, and Asian or Pacific Islander) to five (White, Black or African American, American Indian or Alaska Native, Asian, and Native Hawaiian or Other Pacific Islander). In addition, the revised standards require Federal data collection programs to allow respondents to select more than one race category when responding to a query on their racial identity. This provision means that under the revised standards there are potentially 31 race groups (5 single-race and 26 multiple-race), depending on whether an individual selects one, two, three, four, or all five of the race categories.
Why race bridge? During the transition to full implementation of the 1997 standards (see paragraph below), these two different standards for the collection of race and ethnicity data are both being used, creating incomparability across data systems. Further, within a given data system, the change in the race standards results in incomparability across time, thus making it difficult to perform trend analyses. The OMB recognized that race-bridging approaches would be needed to make race data collected under the 1997 standards comparable to race data collected under the 1977 standards. Therefore, the OMB issued "Provisional Guidance on the Implementation of the 1997 Standards for Federal Data on Race and Ethnicity" (10). The guidance document contains a detailed discussion of various bridging methods.
Why does NCHS use bridged-race population estimates? Vital rates are based on information obtained from vital records collected through the state-based Vital Statistics Cooperative Program (numerators) and population estimates derived from the U.S. Census (denominators). Because of differences in the timing of implementation of the 1997 standards, beginning with the 2000 data year, the numerators and denominators of vital rates have incompatible race data. The question on race on the 2000 census was based on the revised OMB standards and so allowed respondents to select more than one race category. As a result, population estimates for 2000 and beyond have five single-race categories and up to 26 multiple-race categories. Implementation of the 1997 standards within the Vital Statistics Cooperative System started in 2003, on an individual state basis, and is expected to proceed slowly as states implement revised birth and death certificates which incorporate the revised OMB standards. As of 2008, most states had not revised the race question on their birth or death certificates and were still collecting race data using the 1977 race categories. Therefore, at this time, the calculation of post-2000 race-specific birth and death rates requires population estimates with the 1977 race categories. When a sufficient number of states have adopted the revised birth and death certificates, rates will be presented using population estimates that comply with the 1997 standards.
Specifics about NCHS Use of Bridged-Race Population Estimates NCHS publishes national (and some state) birth and death rates on an annual basis. NCHS uses the bridged-race postcensal population estimates to calculate birth and death rates. Vital rates for a given data year are calculated using bridged-race population estimates from the bridged-race estimates series corresponding with that year. For example, vital rates for 2001 were calculated using population estimates from the Vintage 2001 postcensal series, vital rates for 2002 were calculated using estimates from the Vintage 2002 postcensal series, and so forth. Vital rates for postcensal data years are not recalculated using updated postcensal estimates. Rather, NCHS revises rates published for postcensal years only once intercensal population estimates become available. Thus, the vital rates for 1991-1999, which originally were calculated using 1990-based postcensal population estimates, have been recalculated using the bridged-race intercensal population estimates for 1991-1999.
NCHS Regression Bridging Method
Bridging methodology developed by NCHS bridges the multiple-race group population counts to single-race categories (11, 12). Information from the pooled 1997-2000 National Health Interview Survey was used to develop the bridging methodology. Regression models with person-level and county-level covariates were used to generate the probability of selecting each single-race category possible for a multiple-race group. The probabilities generated from the fitted regression models are referred to as the NHIS bridging proportions. The Census Bureau applied the NHIS bridging proportions generated by NCHS to the Census 2000 Modified Race Data Summary file (8). This application resulted in a bridged population count for each of the four single-race categories (White, Black or African American, American Indian or Alaska Native, and Asian or Pacific Islander) by county, single-year of age, Hispanic origin group, and sex, for April 1, 2000. Annually, the bridging proportions are applied to the latest vintage of postcensal estimates with 31 race groups (the 31 race groups used in Census 2000 in accordance with the 1997 OMB standards) to obtain the bridged-race population estimates for the four single-race categories. The bridging methodology is described in detail in the report, "United States Census 2000 Population with Bridged Race Categories" (11).
Bridged-race Postcensal Population Estimates
Postcensal population estimates are estimates made for the years following a census, before the next census has been taken. Postcensal estimates are derived by updating the resident population enumerated in the decennial census using various measures of population change. The components of population change used in the derivation of the postcensal estimates include: births to U.S. resident women, deaths to U.S. residents, net international immigration, net movement of U.S. Armed Forces and civilian citizens of the U.S, and migration within the U.S. The Census Bureau annually produces a series of postcensal estimates that includes estimates for the current data year and revised estimates for earlier years. The last year in a series is used to name the series. For example, the Vintage 2002 postcensal series has estimates for July 1, 2000, July 1, 2001, and July 1, 2002. The Vintage 2003 series has estimates for July 1, 2000, July 1, 2001, July 1, 2002, and July 1, 2003. The July 1, 2000, July 1, 2001, and July 1, 2002 estimates from the Vintage 2002 and Vintage 2003 series differ. Estimates for earlier years in a given series are revised to reflect
- changes in the components of population change data sets (for example, a preliminary natality file is replaced with a final natality file);
- challenges to the population estimates; and
- changes in the estimation methodology.
The Census Bureau annually produces a postcensal series of estimates of the resident population of the United States with 31 race groups (in accordance with the 1997 OMB standards). The Census 2000 Modified Race Data Summary File serves as the base data for these post-2000 postcensal series (13). Under a collaborative arrangement with NCHS, the Population Estimates Program of the U.S. Census Bureau applies the NHIS bridging proportions to the 31-race postcensal population estimates to produce the bridged-race postcensal estimates (estimates for the four single-race categories: White, Black or African American, American Indian or Alaska Native, and Asian or Pacific Islander).
Variance of Bridged-Race Population Estimates
Population estimates generally are assumed to be fixed and do not contribute to the variance of rates. However, this is not true for bridged-race population estimates. Although efforts were made to use the best available data and methods to produce the bridged-race estimates, the modeling process introduces error into the estimates. The potential for error will be greatest for the smallest population groups, particularly the smaller race groups and county level estimates. Methodology to compute variances for bridged-race population estimates has been developed (14).
Release of Bridged-Race Population Estimates
In response to the need for bridged estimates by a wide range of users, NCHS makes the bridged-race population estimates available for download from the web site "U.S. Populations with Bridged Race Categories" (http://www.cdc.gov/nchs/nvss/bridged_race.htm) and also through CDC WONDER online databases (http://wonder.cdc.gov]. The report detailing the bridging methodology, "United States Census 2000 Population with Bridged Race Categories," also is available for download (United States Census 2000 Population with Bridged Race Categories).
Comments and Questions
NCHS would appreciate receiving feedback on the usefulness of the bridged-race estimates as well as notification of any problems that have been identified. Comments or questions about the estimates may be sent via e-mail to:
Suggested Citation
National Center for Health Statistics. Postcensal estimates of the resident population of the United States for July 1, 2000-July 1, 2008, by year, county, age, bridged race, Hispanic origin, and sex (Vintage 2008). Prepared under a collaborative arrangement with the U.S. Census Bureau; released May 14, 2009. Available from: http://www.cdc.gov/nchs/about/major/dvs/popbridge/popbridge.htm as of September 2, 2009.
References
- National Center for Health Statistics. Postcensal estimates of the resident population of the United States for July 1, 2000-July 1, 2008, by year, county, age, bridged race, Hispanic origin, and sex (Vintage 2008). Prepared under a collaborative arrangement with the U.S. Census Bureau; released May 14, 2009. Available from: http://www.cdc.gov/nchs/about/major/dvs/popbridge/popbridge.htm as of September 2, 2009. Now at http://www.cdc.gov/nchs/nvss/bridged_race.htm.
- Office of Management and Budget. Revisions to the standards for the classification of Federal data on race and ethnicity. Federal Register 62FR58781-58790, October 30, 1997. (Available here.)
- Office of Management and Budget. Race and ethnic standards for Federal statistics and administrative reporting. Statistical Policy Directive 15, May 12,1977. (Available here.)
- U.S. Census Bureau. Vintage 2008 estimates: release notes. 2009. (Available here.)
- U.S. Census Bureau. Methodology for the United States resident population estimates by age, sex, race, and Hispanic origin (Vintage 2008): April 1, 2000 to July 1, 2008. 2009. (Available here.)
- U.S. Census Bureau. Methodology for the United States resident population estimates by age, sex, race, and Hispanic origin (Vintage 2007): April 1, 2000 to July 1, 2007. 2008. (Available here.)
- U.S. Census Bureau. Special processing procedures for the areas affected by Hurricanes Katrina and Rita: (Vintage 2008): April 1, 2000 to July 1, 2008. 2009. (Available here or from http://www.census.gov/popest/topics/methodology/2008-hurr-spcl-meth.html).
- U.S. Census Bureau. Special processing procedures for the areas affected by Hurricanes Katrina and Rita: (Vintage 2007): April 1, 2000 to July 1, 2007. 2008. (Available here or from http://www.census.gov/popest/topics/methodology/2007-hurr-spcl-meth.html).
- U.S. Census Bureau. Special population estimates for impacted counties in the Gulf Coast Area. 2008. (Available from http://www.census.gov/Press-Release/www/emergencies/impacted_gulf_estimates.html).
- Office of Management and Budget. Provisional guidance on the implementation of the 1997 standards for the collection of Federal data on race and ethnicity. December 15, 2000. http://www.Whitehouse.gov/omb/inforeg/r&e_guidance2000update.pdf. (Also available here.)
- Ingram DD, Parker JD, Schenker N, Weed JA, Hamilton B, Arias E, Madans JH. United States Census 2000 population with bridged race categories. Vital Health Stat 2 (135). Hyattsville, Maryland: National Center for Health Statistics. 2003. (Available here.)
- Parker JD, Schenker N, Ingram DD, Weed JA, Heck KE, Madans JH. Bridging between two standards for collecting information on race and ethnicity: an application to Census 2000 and vital rates. Public Health Reports 119 (2), p. 192-205. 2004. (Available here.)
- U.S. Census Bureau. Census 2000 Modified Race Data [MR(31)-CO.txt], prepared by the U.S. Census Bureau, 2002. Available on the internet at: http://www.census.gov/popest/archives/files/MR-CO.txt. (Also available here.)
- Schenker, N (2003). "Assessing variability due to race bridging: application to Census counts and vital rates for the Year 2000," J American Statistical Association, 98, 818-828.
File layout for the Bridged-Race Vintage 2008 Postcensal Files, 2000-2008
The Vintage 2008 series (July 1, 2000-July 1, 2008) is available as two multi-year text files (2000-2004 and 2005-2008), as single-year text files (a separate file for each year in the series), and as a SAS file with only the estimates for July 1, 2008. The files contain bridged-race postcensal estimates of the July 1 resident population of the United States by year, county, single-year of age (0, 1, ..., 85 years and over), bridged-race category (White, Black or African American, American Indian or Alaska Native, Asian or Pacific Islander), Hispanic origin (not Hispanic or Latino, Hispanic or Latino), and sex. There is a record on the files for each combination of county, age, race, sex, and Hispanic origin. The population estimates on the files were derived by the U.S. Census Bureau using the Census 2000 Modified Race Data Summary File as the base file (13). The files were released by NCHS on September 2, 2009
Control totals for Vintage 2008 data files:
Control total File name Number of records* Month, Year Population count pcen_v2008y0004.txt 4,323,392 July 1, 2000 282,171,936 July 1, 2001 285,039,803 July 1, 2002 287,726,647 July 1, 2003 290,210,914 July 1, 2004 292,892,127 Pcen_v2008.y0508.txt 4,323,392 July 1, 2005 295,560,549 July 1, 2006 298,362,973 July 1, 2007 301,290,332 July 1, 2008 304,059,724 pcen_v2008_y00.txt 4,323,392 July 1, 2000 282,171,936 pcen_v2008_y01.txt 4,323,392 July 1, 2001 285,039,803 pcen_v2008_y02.txt 4,323,392 July 1, 2002 287,726,647 pcen_v2008_y03.txt 4,323,392 July 1, 2003 290,210,914 pcen_v2008_y04.txt 4,323,392 July 1, 2004 292,892,127 pcen_v2008_y05.txt 4,323,392 July 1, 2005 295,560,549 pcen_v2008_y06.txt 4,323,392 July 1, 2006 298,362,973 pcen_v2008_y07.txt 4,323,392 July 1, 2007 301,290,332 pcen_v2008_y08.txt 4,323,392 July 1, 2008 304,059,724 pcen_v2008_y08.sas7bdat 4,323,392 July 1, 2008 304,059,724* One record for each county, race, sex, Hispanic origin, and age combination.
File Layout for pcen_v2008.y0004.txt:
Location Field size Item and Code Outline Format 1-4 4 Series vintage (2008) Numeric 5-6 2 FIPS State code Numeric 7-9 3 FIPS county code Numeric 10-11 2 Age Numeric (0, 1, 2,..., 85 years and over) 12 1 Race-sex Numeric 1=White male 2=White female 3=Black male 4=Black female 5=American Indian or Alaska Native male 6=American Indian or Alaska Native female 7=Asian or Pacific Islander male 8=Asian or Pacific Islander female 13 1 Hispanic origin Numeric 1=not Hispanic or Latino 2=Hispanic or Latino 14-21 8 Population count July 1, 2000 Numeric 22-29 8 Population count July 1, 2001 Numeric 30-37 8 Population count July 1, 2003 Numeric 46-53 8 Population count July 1, 2004 Numeric
File Layout for pcen_v2008.y0508.txt:
Location Field size Item and Code Outline Format 1-4 4 Series vintage (2008) Numeric 5-6 2 FIPS State code Numeric 7-9 3 FIPS county code Numeric 10-11 2 Age Numeric (0, 1, 2,..., 85 years and over) 12 1 Race-sex Numeric 1=White male 2=White female 3=Black male 4=Black female 5=American Indian or Alaska Native male 6=American Indian or Alaska Native female 7=Asian or Pacific Islander male 8=Asian or Pacific Islander female 13 1 Hispanic origin Numeric 1=not Hispanic or Latino 2=Hispanic or Latino 14-21 8 Population count July 1, 2005 Numeric 22-29 8 Population count July 1, 2006 Numeric 30-37 8 Population count July 1, 2007 Numeric 46-53 8 Population count July 1, 2008 Numeric
File Layout for
Location Field size Item and Code Outline Format
1-4 4 Series vintage (2005) Numeric
5-6 2 FIPS State code Numeric
7-9 3 FIPS county code Numeric
10-11 2 Age Numeric
(0, 1, 2,..., 85 years and over)
12 1 Race-sex Numeric
1=White male
2=White female
3=Black male
4=Black female
5=American Indian or Alaska Native male
6=American Indian or Alaska Native female
7=Asian or Pacific Islander male
8=Asian or Pacific Islander female
13 1 Hispanic origin Numeric
1=not Hispanic or Latino
2=Hispanic or Latino
14-21 8 July 1, Population count estimate Numeric
file y00 has estimate for July 1, 2000
file y01 has estimate for July 1, 2001
file y02 has estimate for July 1, 2002
file y03 has estimate for July 1, 2003
file y04 has estimate for July 1, 2004
file y05 has estimate for July 1, 2005
file y06 has estimate for July 1, 2006
file y07 has estimate for July 1, 2007
file y08 has estimate for July 1, 2008
The SAS data set, pcen_v2008_y08.sas7bdat
Variable Item and Code Outline Format VINTAGE Series Vintage (2005) Numeric ST_FIPS State FIPS code Numeric CO_FIPS County FIPS code Numeric AGE Age Numeric (0, 1, 2, ..., 85 years and over) RACESEX Race Numeric 1=White male 2=White female 3=Black male 4=Black female 5=American Indian or Alaska Native male 6=American Indian or Alaska Native female 7=Asian or Pacific Islander male 8=Asian or Pacific Islander female SEX Sex Numeric 1=male 2=female HISP Hispanic origin Numeric 1=not Hispanic or Latino 2=Hispanic or Latino Pop July 1, 2008 resident population Numeric
Source:
Documentation for bridged-race postcensal Vintage 2008 population estimates for July 1, 2000-July 1, 2008, which was released on September 2, 2009 is on the internet at ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Datasets/NVSS/bridgepop/2008/DocumentationBridgedPostcenV2008.pdf.