Bridged-Race Population Estimates for Census 2000 and 2010
Starting in the 2000 decennial census, the U.S Census Bureau has used the 1997 Office of Management and Budget (OMB) revised standards for the classification of Federal data on race and ethnicity. Thus, race data on the 2000 and 2010 census are not comparable with race data from data systems that continue to collect data using the 1977 OMB standards. The 1977 standards specified four single-race categories: American Indian or Alaska Native, Asian or Pacific Islander, black, and white. The 1997 standards required that Federal data collection programs allow respondents to select one or more race categories when responding to a query on their racial identity. This provision means that there are potentially 31 race groups, depending on whether an individual selects one, two, three, four, or all five of the race categories. For comparability, the National Center for Health Statistics (NCHS), in collaboration with the U.S. Census Bureau, developed methodology to bridge the race groups in Census 2000 and 2010 to the four single-race categories specified under the 1977 standards. Even though Federal programs were to fully implement the revised standards by January 1, 2003, the transition from the 1977 to the 1997 OMB standards has been uneven. Federal systems which rely on information obtained from vital records through state-based programs, such as the National Vital Statistics System, have not yet been able to fully implement the 1997 standards. For example, the U.S. standard birth and death certificates were revised in 2003 to include the 1997 OMB standards. However, as of 2011, 41 states, New York City, and the District of Columbia had adopted the 2003 U.S. standard birth certificate, and 36 states, New York City, and the District of Columbia had adopted the 2003 U.S. standard death certificate.
MethodologyThe bridging methodology was developed using information from the 1997-2000 National Health Interview Survey (NHIS). The NHIS provides a unique opportunity to investigate multiple-race groups because, since 1982, it has allowed respondents to choose more than one race but has also asked respondents reporting multiple races to choose a primary race. The bridging methodology developed by NCHS involved the application of regression models relating person-level and county-level covariates to the selection of a particular primary race by the multiple-race respondents. Bridging proportions derived from these models were applied by the U.S. Census Bureau to the Census 2000 Modified Race Data Summary file. This application resulted in bridged counts of the April 1, 2000 and April 1, 2010 resident single-race populations for the four racial groups specified in the 1977 OMB standards.
National Vital Statistics System-Mortality (NVSS-M)
Vital statistics mortality data are a fundamental source of demographic, geographic, and cause-of-death information. This is one of the few sources of comparable health-related data for small geographic areas over an extended time period. The data are used to present characteristics of those dying in the United States, to determine life expectancy, and to compare mortality trends with those in other countries.
MethodologyThe National Vital Statistics System Mortality component (NVSS-M) obtains information on deaths from the registration offices of each of the 50 states, New York City, the District of Columbia, Puerto Rico, the U.S. Virgin Islands, Guam, American Samoa, and Northern Mariana Islands. By law, registration of deaths is the responsibility of the funeral director. The funeral director obtains demographic data from an informant. The physician in attendance at the death is required to certify the cause of death. When death is from other than natural causes, a coroner or medical examiner may be required to examine the body and certify cause. State death certificates are modeled on a U.S. Standard Certificate that is revised periodically. States provide the National Center for Health Statistics (NCHS) with death records in electronic format.
Postcensal population estimates are estimates made for the years following a census, before the next census has been taken. National postcensal population estimates are derived annually by updating the resident population enumerated in the decennial census using a components of population change approach. Each annual series includes estimates for the current data year and revised estimates for the earlier years in the decade. The U.S. Census Bureau also produces postcensal estimates of the resident population for each state and county by using a component of population change method at the county level. An additional component of population change, net internal migration, is involved. The state population estimates are produced by summing all county populations within each state. The Census Bureau has annually produced a postcensal series of estimates of the July 1 resident population of the United States based on Census 2000 by applying the components of change methodology to the Modified Race Data Summary file. So that the race data for 2000-based postcensal estimates will be comparable with race data on vital records, the Census Bureau has applied the National Health Interview Survey (NHIS) bridging methodology to each 31-race-group postcensal series of population estimates to obtain bridged-race postcensal estimates (estimates for the four single-race categories: American Indian or Alaska Native, Asian or Pacific Islander, black, and white).Vital rates for 2000 were calculated using the bridged-race April 1, 2000, census counts, and vital rates for 2001 and beyond were calculated using bridged-race estimates of the July 1 population from the corresponding postcensal vintage. Intercensal population estimates are estimates made for the years between two censuses and are produced once the decennial census at the end of the decade has been completed. They replace the postcensal estimates that were produced prior to the completion of the census at the end of the decade. Intercensal estimates are more accurate than postcensal estimates because they are based on both the census at the beginning and the census at the end of the decade and thus correct for the error of closure (the difference between the estimated population at the end of the decade and the census count for that date).
MethodologyThe following formula is used to derive the estimates for a given year from those for the previous year, starting with the decennial census enumerated resident population as the base: Resident population+ Births to U.S. resident women - Deaths to U.S. residents+ Net international migration. The postcensal estimates are consistent with official decennial census figures and do not reflect estimated decennial census under-enumeration. Estimates for the earlier years in a given series are revised to reflect changes in the components of change data sets (for example, births to U.S. resident women from a preliminary natality file are replaced with counts from a final natality file). To help users keep track of which postcensal estimate is being used, each annual series is referred to as a vintage and the last year in the series is used to name the series. For example, the Vintage 2001 postcensal series has estimates for July 1, 2000, and July 1, 2001, and the Vintage 2002 postcensal series has revised estimates for July 1, 2000, and July 1, 2001, as well as estimates for July 1, 2002. The estimates for July 1, 2000, and for July 1, 2001, from the Vintage 2001 and Vintage 2002 postcensal series, differ. Vital rates that were calculated using postcensal population estimates are routinely revised when intercensal estimates become available.