|
2002 ESTIMATES AND PROJECTIONS AREA METHODOLOGY
STATE AND COUNTY TOTAL POPULATION ESTIMATES
BACKGROUND
The U.S. Census Bureau produces estimates of total resident population for each
state and county on an annual basis. County population estimates are produced
with a component of population change method, while the state population estimates
are solely the sum of the county populations. The following documentation
describes the work that is being carried out in the production of the July 1,
2002 total resident population estimates at the county level.
OVERVIEW
The Census Bureau develops county population estimates with a demographic
procedure called an "administrative records component of population
change" method. A major assumption underlying this approach is that the
components of population change can be closely approximated by administrative
data in a demographic change model. In order to apply the model, Census Bureau
demographers estimate each component of population change separately. For the
population residing in households the components of population change are births,
deaths and net migration, including net international migration. For the
non-household population, change is represented by the net change in the
population living in group-quarters facilities.
Each component in our model is represented with data that are symptomatic of some
aspect of population change. For example, birth certificates are symptomatic of
additions to the population resulting from births, so we use these data to
estimate the birth component for a county. Some other components are derived
from death certificates, Internal Revenue Service data (IRS), Medicare enrollment
records, Armed Forces data, group-quarters population data, and the American
Community Survey (ACS).
In cases where we do not have data for all counties for the current estimate
year, we estimate the components of population change based on one or more
simplifying assumptions. When we prepare our initial population estimates, we
use the same variant of the component model with these simplifying assumptions.
In the creation of current vintage population estimates, we replace the initial
population estimates from the previous vintage with "revised"
population estimates calculated with the actual data for all components of
population change. Calculations of "revised" population estimates also
incorporate updates to components of change from previous years.
METHOD
We produce the estimates of the county populations, starting with the base
populations from either Census 2000 or the revised population estimate for the
most recent year and then add or subtract the demographic components of population
change calculated for the time period. Basically, we add the estimated number
of births and subtract the estimated number of deaths for the time period. We
then account for net migration, which is calculated using several components
including: net internal migration, net foreign-born international migration, net
movement to/from Puerto Rico, net movement of federal and civilian citizens, the
change in group-quarters population, and native emigration from the United States.
We produce separate population estimates for the populations under age 65 and
age 65 and older, mainly because different data are used to measure the internal
migration of these two populations. For the population under age 65, we use
data from individual IRS tax returns to calculate measures of migration. Because
the population age 65 and older is not always well-represented on tax returns,
we need to use a different source (Medicare enrollment) to calculate measures of
migration for this population. The following describes how we produce population
estimates for these two populations.
STEP 1: ESTIMATING THE POPULATION UNDER AGE 65
1A. |
Base Populations
1A-1. Total base population under age 65 -
The total base population for the estimate of the population under age
65 is either the April 1, 2000 population estimates base or the revised
county population estimate for the prior estimate year. For official
population estimates, the April 1, 2000 population estimates base is not
adjusted for census undercount.
In general, the April 1, 2000 population estimates base uses Census 2000
data as its base, but includes certain modifications (geographic updates,
Count Question Resolution (CQR) changes, and updates to Tiger).
1A-2. Base group-quarters population under age 65 -
The group-quarters population component is primarily a combination of
military personnel living in barracks, college students living in
dormitories and persons residing in institutions. Inmates of correctional
facilities, persons in health care facilities and persons in Job Corps
Centers are also included in this category. We have excluded persons
age 65 and older residing in nursing homes and other facilities from this
category since they are included in the estimate of the population age
65 and older. The base group-quarters population for the current
estimate year is the revised group-quarters population from the prior
estimate year. In the first estimate year following the decennial
census, the base group-quarters population is the group-quarters
population as enumerated in Census 2000.
1A-3. Base household population under age 65 -
After we subtract the base group-quarters population under age 65 from
the base total population under age 65 we have a residual that we call
the base household population under age 65 by county. The general
formula is as follows:
U65HPx-1 = ARESTx-1
- (EX64x-1 + EPO65x-1
+ GQ<65x-1)
| Where: |
|
| U65HP |
is the county base household population under age 65 |
| AREST |
is the total county population for all ages |
| EPO65 |
is the county population age 65 and older |
| GQ<65 |
is the county group-quarters population under age 65 |
| EX64 |
is the county population age 64 in the previous estimate year
(who will turn age 65 in the current estimate year). The process
of estimating the population aged 64 years old for counties is
achieved through the following formula:
EX64x-1 = SX64x-1
* (TR_64x-1 / UX64x-1)
| Where: |
|
| EX64 |
is the county population age 64 in the previous estimate
year (who will turn age 65 in the current estimate year) |
| SX64 |
is the total county population under age 65 in the
previous estimate year |
| TR_64 |
is the total national population age 64 in the previous
estimate year |
| UX64 |
is the total national population under age 65 in the
previous estimate year |
|
Note: In the above formulas - |
| x-1 |
denotes the previous estimate year |
1A-4. Population base of potential internal migrants under age 65 -
The population base of potential internal migrants is usually
considered to be the midpoint population of the period since the
population at the beginning of the estimate period has not yet
experienced the births and deaths that are reflected in the
population at the end of the period. Also, the population at the
end of the estimate period includes in-migrants and excludes
out-migrants. The best compromise is to take the population at the
midpoint of the period.
Estimated resident births, estimated deaths to people under age 65,
and net international migration are assumed to have been evenly
distributed throughout the estimate interval and, therefore, have
the potential for migration, on average, for one-half of the period.
We develop the internal migration base under age 65 by adding one
half of the following to the household base population under 65
years: estimated resident births minus estimated resident deaths
under 65 years, plus estimated net international migration. The
base internal migration population under age 65 is calculated using
the following formula:
MBASE<65x = U65HPx-1
+ (.5 * (PBx -
PD<65x + INAT<65x
- EMIG<65x +
NMPR<65x))
| Where: |
|
| MBASE<65 |
is the county population base of potential internal migrants
under age 65 |
| U65HP |
is the county base household population under age 65 |
| PB |
are the county-level period births |
| PD<65 |
are the county-level period deaths to the population under age 65 |
| INATT<65 |
is the county net international migration under age 65 |
| EMIG<65 |
is the county native emigration of the population under age 65 |
| NMPR<65 |
is the county net movement to/from Puerto Rico under age 65 |
Note: In the above formula - |
| x |
denotes the current estimate year |
| x-1 |
denotes the previous estimate year |
|
1B. |
Components of population change
1B-1. Resident births - Resident births are
recorded by residence of mother, regardless of where the birth occurred;
hence, a county need not have a hospital in order to have resident births.
1B-2. Resident deaths to population under age 65 -
We use death data tabulated by the most recent residence of the decedent,
not by the place where death occurred.
1B-3. Net internal migration for population under age 65 -
We estimate the net internal migration within the United States during
the estimate interval. Our estimate includes household migration derived
from individual Federal income tax returns and the change in the
group-quarters population.
1B-3a. Migration from Federal Income Tax Returns -
We use data from individual Federal income tax returns supplied by the
Internal Revenue Service (IRS) to measure part of the internal migration
of the population under age 65. These data are limited to filers and
their dependents who are under age 65. We derive net internal migration
rates using these data and then apply these rates to the household
population under age 65.
Part 1. Internal Migration Rate - The net
internal migration rate for the household population under age 65 for
each county is calculated using the following formula, which is based on
the difference between the in-migration and out-migration of tax filers
and their dependents:
NiMR<65x =
[(INSTx +
INCTYx +
INFORx) -
(OUTSTx +
OUTCTYx +
OUTFORx)] /
(NONx +
OUTSTx +
OUTCTYx +
OUTFORx)
| Where: |
|
| NiMR<65 |
is the county net internal migration rate for the household
population under age 65 |
| INST |
are the county in-migrants from another state |
| INCTY |
are the county in-migrants from another county within the same state |
| INFOR |
are the county in-migrants from a foreign location |
| OUTST |
are the county out-migrants to another state |
| OUTCTY |
are the county out-migrants to another county within the same state |
| OUTFOR |
are the county out-migrants to a foreign location |
| NON |
are the county nonmigrants |
Part 2. Net internal migration - Net
migration for the population under age 65 is the product of the net
internal migration rate (NiMR<65) and the base internal migration
population under age 65, as calculated using the following formula:
MIG<65x =
(MBASE<65x *
NiMR<65x) -
FEDCIV<65x
| Where: |
|
| MIG<65 |
is the county net internal migration of the household population
under age 65 |
| MBASE<65 |
is the county population base of potential internal migrants
under age 65 |
| NiMR<65 |
is the county net internal migration rate for the household
population under age 65 |
| FEDCIV<65* |
is the county net federal and civilian citizen movement under age 65 |
If the net migration (MIG<65) is negative (-), then the figure
indicates net out-migration of the household population; otherwise, the
figure represents net in-migration.
* The net internal migration rate for the household population under age
65 (NiMR<65) includes in- and out-migrations to/from a foreign location.
Our assumption is that the in- and out-migrants to/from a foreign location
who file independent tax returns are mostly federal and civilian citizens.
Therefore, we take the federal and civilian citizen movement component for
the population under age 65 (FEDCIV<65) out of the net internal
migration of the household population under age 65 (MIG<65). See
section 1B-4 for a description of how we calculate FEDCIV<65.
1B-3b. Migration from Change in Group-Quarters Population -
We use data on the change in the group-quarters population to measure
part of the internal migration of the population under age 65. We use
group-quarters population data from two sources to estimate county
populations: (1) Census 2000 counts of group-quarters population by
single year of age and facility type for each subcounty area, and
(2) a time series of individual group-quarters records from the
Group Quarters Report (GQR). Subcounty areas are commonly referred to
as places, cities, towns, etc. These areas represent functioning
governmental units and residual pieces thereof.
These two sets of group-quarters population data are used to derive a
time series of group-quarters population through the following process:
Part 1. We sum the group-quarters populations from
Census 2000 (total under age 65 only) and the GQR to the subcounty level
by the seven facility types for each estimate date in the time series.
Part 2. We derive the total group-quarters population
under age 65 by GQ type from the summarized GQR data using age
distribution data from Census 2000 in the following formula:
GQR<65x,t =
(GQ<65C2000,t /
GQC2000,t) *
GQRTOTx,t
| Where: |
|
| GQR<65 |
is the subcounty GQR population under age 65 |
| GQ<65 |
is the subcounty group-quarters population under age 65 |
| GQ |
is the subcounty group-quarters population of all ages |
| GQRTOT |
is the subcounty GQR population of all ages |
Part 3. The time series of subcounty group-quarters
population under age 65 by GQ type is then calculated by adding the year
to year change given by the GQR data, using the following formula:
GQ<65x,t =
GQ<65x-1,t +
(GQR<65x,t -
GQR<65x-1,t)
| Where: |
|
| GQR<65 |
is the subcounty GQR population under age 65 |
| GQ<65** |
is the subcounty group-quarters population under age 65 |
** Is the Census 2000 GQ population for the July 1, 2000 estimate
Part 4. The subcounty numbers are summed to the county
level for the calculation of county population estimates.
Note: In the above formulas-
| C2000 |
denotes a Census 2000 reference date |
| x |
denotes the current estimate year |
| x-1 |
denotes the previous estimate year |
| t |
denotes facility type (correctional institutions, juvenile
facilities, nursing homes, other institutional, university
dormitories, military barracks, other noninstitutional) |
1B-4. Net foreign-born international migration for population under age 65 -
1B-4a. Net foreign-born international migration -
National-level data on the net foreign-born international migration of
the population under age 65 for the current estimate period are
distributed to counties based on the county distribution of the
foreign-born population who entered the U.S. during the 5 years prior to
April 1, 2000 by country of birth from Census 2000 using the
following formula:
FBINAT<65NAT,x =
NFBINAT<65NAT,x *
(FB<65NAT,C2000 /
NFB<65NAT,C2000)
| Where: |
|
| FBINAT<65 |
is the county net foreign-born international migration under age
65 by country of birth |
| NFBINAT<65 |
is the national net foreign-born international migration under
age 65 by country of birth |
| FB<65 |
is the county foreign-born population under age 65 who entered
the U.S. during the five years prior to April 1, 2000 by country
of birth |
| NFB<65 |
is the national foreign-born population under age 65 who entered
the U.S. during the five years prior to April 1, 2000 by country
of birth |
The county foreign-born international migration under age 65 by country
of birth are then summed to derive the total county foreign-born
international migration under age 65.
1B-4b. Net movement from Puerto Rico - National-level
data on the total net movement of the population under age 65 to or from
Puerto Rico for the current estimate period are distributed to counties
based on the county distribution of the Puerto Rican population from
Census 2000 using the following formula:
NMPR<65x =
NATNMPR<65x *
(PR<65C2000 /
NATPR<65C2000)
| Where: |
|
| NMPR<65 |
is the county net movement to/from Puerto Rico under age 65 |
| NATNMPR<65 |
is the national net movement to/from Puerto Rico under age 65 |
| PR<65 |
is the county population under age 65 from Puerto Rico |
| NATPR<65 |
is the national population under age 65 from Puerto Rico |
1B-4c. Federal and civilian citizen movement -
National-level data on the total federal and civilian citizen movement
of the population under age 65 for the current estimate period are
derived using a two-stage distribution process, using the national-level
data and station strength data (the number of Armed Forces personnel
stationed at military bases) - originally supplied by the each branch of
the Armed Forces. The final step is to control the county-level data to
the national-level data. The formulas for this process are:
Part 1. Distribute the national total to states using
the proportion of state-level station strength to national-level station
strength using the following formula:
SFEDCIV<65x =
NFEDCIV<65x *
( SSx /
NSSx)
| Where: |
|
| SFEDCIV<65 |
is the state net federal and civilian citizen movement under age 65 |
| NFEDCIV<65 |
is the national net federal and civilian citizen movement under age 65 |
| SS |
is the state station strength |
| NSS |
is the national station strength |
Part 2. Distribute the state totals to counties using
the Armed Forces military employment data from Census 2000 using the
following formula:
FEDCIV<65x =
SFEDCIV<65x *
(MILEMPC2000 /
SMILEMPC2000)
| Where: |
|
| FEDCIV<65 |
is the county net federal and civilian citizen movement under age 65 |
| SFEDCIV<65 |
is the state net federal and civilian citizen movement under age 65 |
| MILEMP |
is the county Armed Forces military employment |
| SMILEMP |
is the state Armed Forces military employment |
Part 3. Raking with a factor is used to ensure
consistency between county FEDCIV<65 and independently produced
national FEDCIV<65. The factor is the national FEDCIV<65 divided
by the sum of all county FEDCIV<65 in the U.S. This factor is
multiplied by each county FEDCIV<65.
1B-4d. Native emigration from the United States -
National-level data on the total number of emigrants from the United
States under age 65 for the current estimate period are distributed to
counties based on the county distribution of the foreign-born population
from Census 2000 using the following formula:
EMIG<65x =
NATEMIG<65x *
(FOR<65C2000 /
NATFOR<65C2000)
| Where: |
|
| EMIG<65 |
is the county native emigration of the population under age 65 |
| NATEMIG<65 |
is the national native emigration of the population under age 65 |
| FOR<65 |
is the county foreign-born population under age 65 who entered
the U.S. during the five years prior to April 1, 2000 |
| NATFOR<65 |
is the national foreign-born population under age 65 who entered
the U.S. during the five years prior to April 1, 2000 |
|
Note: In the above formulas - |
| C2000 |
denotes a Census 2000 reference date |
| x |
denotes estimate year |
| NAT |
denotes country of birth |
|
1C. |
Calculating the Population Under Age 65
The formula for estimating the county population under age 65 from the
base populations and the components of population change is as follows:
U65x =
U65HPx-1 +
PBx -
PD<65x +
MIG<65x +
GQ<65 + INAT<65x -
EMIG<65x +
NMPR<65x +
FEDCIV<65x
| Where: |
|
| U65 |
is the total county population under age 65 |
| U65HP |
is the county base household population under age 65 |
| PB |
are the county-level period births |
| PD<65 |
are the county-level period deaths to the population under age 65 |
| MIG<65 |
is the county net internal migration of the household population
under age 65 |
| GQ<65 |
is the county group-quarters population under age 65 |
| INAT<65 |
is the county net international migration under age 65 |
| EMIG<65 |
is the county native emigration of the population under age 65 |
| NMPR<65 |
is the county net movement to/from Puerto Rico under age 65 |
| FEDCIV<65 |
is the county net federal and civilian citizen movement under age 65 |
Note: In the above formula - |
| x |
denotes the current estimate year |
| x-1 |
denotes the previous estimate year |
Note: All components of population change are rounded to the nearest
whole number. Where applicable, the differences between the sum of
rounded components and the independently produced national components
are added to or subtracted from the components for Los Angeles County,
California (county with the greatest population in the U.S.). |
STEP 2: ESTIMATING THE POPULATION AGE 65 AND OLDER
2A. |
Base Populations
2A-1. Base total population age 65 and older - The
total base population for the estimate of the population age 65 and older
is either the Census 2000 base (for July 1 population estimate in the
decennial year) or the revised county population estimate for the prior
estimate year. See section 1A-1 for a more detailed explanation of the
changes to the Census 2000 base population.
2A-2. Base group-quarters population age 65 and older -
This component is primarily a combination of persons age 65 and older
residing in nursing homes and other facilities and persons residing in
institutions. Inmates of correctional facilities, persons in health
care facilities, military personnel living in barracks, and persons in
Job Corps Centers are also included in this category. The base
group-quarters population for the current estimate year is the revised
group-quarters population from the prior estimate year. In the first
estimate year following the decennial census, the base group-quarters
population is the group-quarters population as enumerated in Census 2000.
2A-3. Base household population age 65 and older -
After we subtract the base group-quarters population age 65 and older
from the base total population age 65 and older, we have a residual that
we call the base household population age 65 and older. The basic formula
is as follows:
O65HPx-1 =
EPO65x-1 +
EX64x-1 -
GQ65+x-1
| Where: |
|
| O65HP |
is the county base household population age 65 and older |
| EPO65 |
is the county population age 65 and older |
| EX64 |
is the county population age 64 in the previous estimate year
(who will turn age 65 in the current estimate year). |
| GQ65+ |
is the group-quarters population age 65 and older |
In the above formula - |
| x-1 |
denotes the previous estimate year |
2A-4. Population base of potential internal migrants age 65 and older -
This population is derived using a slight modification of the calculation
as used for the population under age 65***. See section 1A-4 for a more
detailed description. The basic formula is as follows:
*** These modifications are made because we assume that net international
migration age 65and older are not represented in the Medicare enrollment
data used to derive the internal migration rate for the population age
65 and older.
OBASE65+x =
O65HPx-1 + (.5 *
(FEDCIV65+x -
PD65+x -
EMIG65+x +
NMPR65+x)
| Where: |
|
| OBASE65+ |
is the county population base of potential internal migrants age
65 and older |
| O65HP |
is the county base household population age 65 and older |
| FEDCIV65+ |
is the county net federal and civilian citizen movement age 65
and older |
| PD65+ |
are the county-level period deaths to the population age 65 and
older |
| EMIG65+ |
is the county native emigration of the population age 65 and older |
| NMPR65+ |
is the county net movement to/from Puerto Rico age 65 and older |
Note: In the above formula - |
| x |
denotes the current estimate year |
| x-1 |
denotes the previous estimate year |
|
2B. |
Components of population change
2B-1. Resident deaths to population age 65 and older -
We use death data tabulated by the most recent residence of the decedent,
not by the place where death occurred.
2B-2. Net internal migration for population age 65 and older -
We estimate the net internal migration within the United States during
the estimate interval. Our estimate includes household migration derived
from Medicare enrollment records and the change in the group-quarters
population.
2B-2a. Migration from Medicare Enrollment - We use the
tabulations of the number of Medicare enrollees in each county obtained
from the Centers for Medicare and Medicaid Service (CMS) to calculate
the net internal migration rate. Comparable to IRS data used for the
population under age 65, Medicare enrollment data allow us to develop a
separate estimate of internal migration for the population age 65 and
older.
Part 1. Internal Migration Rate - We derive a net
internal migration rate (NiMR65+) for the household population age 65
and older for each county, which is based on the difference between the
in-migration and out-migration of Medicare enrollees using the following
formula:
NiMR65+ = {MEDX-
[MEDX-1 +
(EX64x +
FEDCIV65+X +
NMPR65+X -
EMIG65+X -
PD65+X) * MEDCOV])} /
MEDX-1
| Where: |
|
| NiMR65+ |
is the county net internal migration rate for the household
population age 65 and older |
| MED |
is the county number of Medicare enrollees |
| EX64 |
is the county population age 64 in the estimate year (who will
turn age 65 in the current estimate year) |
| FEDCIV65+ |
is the county net federal and civilian citizen movement age 65
and older |
| NMPR65+ |
is the county net movement to/from Puerto Rico age 65 and older |
| EMIG65+ |
is the county native emigration of the population age 65 and older |
| PD65+ |
are the county-level period deaths to the population age 65 and older |
| MEDCOV |
is the Medicare coverage rate which is calculated using the
following formula:
MEDCOV = MED2000 / POP65+C2000
| Where: |
|
| MED |
is the county number of Medicare enrollees |
| POP65+ |
is the county population age 65 and older |
|
Part 2. Net internal migration - net migration for the
population age 65 and older is the product of the net internal migration
rate (NiMR65+) and the base internal migration population age 65 and
older minus the federal and civilian citizen movement, net movement from
Puerto Rico plus the native emigration.
MIG65+x =
(OBASE65+x *
NiMR65+x) -
(FEDCIV65+x +
NMPR65+x -
EMIG65+x)
| Where: |
|
| MIG65+ |
is the county internal migration of the household population age
65 and older |
| OBASE65+ |
is the county population base of potential internal migrants age
65 and older |
| NiMR65+ |
is the county net internal migration rate for the household
population age 65 and older |
| FEDCIV65+ |
is the county net federal and civilian citizen movement age 65
and older |
| NMPR65+ |
is the county net movement to/from Puerto Rico age 65 and older |
| EMIG65+ |
is the county native emigration of the population age 65 and older |
Note: In the above formulas - |
| x |
denotes the current estimate year |
| x-1 |
denotes the previous estimate year |
| C2000 |
denotes a Census 2000 reference date |
| 2000 |
denotes a calendar year 2000 reference date |
If the net migration (MIG65+) is preceded by a minus sign (-), then the
figure indicates net out-migration; otherwise, the figure represents net
in-migration.
2B-2b. Migration from Change in Group-Quarters Population -
The process we use to derive the group quarters change for the population
age 65 and older is similar to that used for the population under age 65.
See section 1B-3 for a more detailed description.
2B-3. Net foreign-born international migration for population
age 65 and older - The process we use to derive the international
migration for the population age 65 and older is similar to that used for
the population under age 65. See section 1B-4 for a more detailed
description. |
2C. |
Calculating the Population Age 65 and Older
The formula for estimating the county population age 65 and older from
the base population and the components of population change is as
follows:
O65x =
065HPx-1 -
PD65+x +
MIG65+x +
GQ65+x +
INAT65+x -
EMIG65+x +
NMPR65+x +
FEDCIV65+x
| Where: |
|
| O65 |
is the total county population age 65 and older |
| O65HP |
is the county base household population age 65 and older |
| PD65+ |
are the county-level period deaths for the population age 65 and older |
| MIG65+ |
is the county internal migration of the household population age
65 and older |
| GQ65+ |
is the county group-quarters population age 65 and older |
| INAT65+ |
is the county net international migration age 65 and older |
| EMIG65+ |
is the county native emigration of the population age 65 and older |
| NMPR65+ |
is the county net movement to/from Puerto Rico age 65 and older |
| FEDCIV65+ |
is the county net federal and civilian citizen movement age 65
and older |
Note: In the above formula - |
| x |
denotes the current estimate year |
| x-1 |
denotes the previous estimate year |
Note: All components of population change are rounded to the nearest
whole number. Where applicable, the differences between the sum of
rounded components and the independently produced national components
are added to or subtracted from the components for Los Angeles County,
California (county with the greatest population in the U.S.). |
STEP 3: CALCULATING THE TOTAL POPULATION
3A. |
Raking the populations
Raking with a factor is used to ensure consistency between county
population estimates and independent estimates of the national population.
3A-1. Raking the population under age 65 - The factor
is the national estimate of the total population under age 65 divided by
the sum of the estimated total population under age 65 for all counties
in the nation. This factor is multiplied by each county population under
age 65.
3A-2. Raking the population age 65 and older - The
factor is the national estimate of the total population aged 65 and older
divided by the sum of the estimated total population aged 65 and older
for all counties in the nation. This factor is multiplied by each county
population age 65 and older. |
3B. |
Rounding the populations
After applying the factors to the populations under age 65 and age 65
and older, we may have population estimates with fractional results. To
eliminate "fractional people", we round the population estimate to the
nearest whole number. Where applicable, the differences between the sum
of rounded population estimates and the independently produced national
population estimates are added to or subtracted from the population for
Los Angeles County, California (county with the greatest population in
the U.S.). |
3C. |
Administrative components of population change (ACOC)
These changes include results of challenges to population estimates,
special censuses, test censuses, and dress rehearsal censuses. |
3D. |
Calculating the Total Population
The total population for each county is the sum of the raked population
under age 65 and the raked population age 65 and older. And again, the
total population for each state is the sum of the county populations in
that state. |
SPECIAL SECTION: ESTIMATING THE THREE-MONTH PERIOD
The population estimate for the three-month period between April 1 and July 1
of the decennial census year is produced using the same method as above, but
incorporates three-months of data instead of a full-year of data. The
three-months of data are derived by taking one-quarter of the data for the
period July 1, 1999 to June 30, 2000. The only exception to this approach is
the group-quarters population - for which we assume no change in the April 1
group-quarters population and it is held constant until July 1. |
