Current Population Survey Design and Methodology - Census Bureau

applied to equation (2). This fact obviates measuring institutionalized
inmate deaths or deaths of the Armed Forces
members residing in the United States.
where IM = net international migration in the time interval
(t 0,t 1).
At this point, we restate equation (2) to incorporate equations
(3), (4), and (5), and simplify. The resulting equation,
which follows, is the operational equation for population
change in the civilian noninstitutionalized population universe.
PCNt1 = PCNt0 + B − D + IM −
(WWAFt1 − WWAFt0 + DAFO − NRO) −(PCIt1 − PCIt0) (6)
Equation (6) identifies all the components that must be
separately measured or projected to update the total civilian
noninstitutionalized population from a base date to a
later reference date.
Aside from forming the procedural basis for all estimates
and projections of total population (in whatever universe),
balancing equations (1), (2), and (6) also define a recursive
concept of internal consistency of a population series
within a population universe. We consider a time series of
population estimates or projections to be internally consistent
if any population figure in the series can be derived
from any earlier population figure as the sum of the earlier
population and the components of population change for
the interval between the two reference dates.
Measuring the Components of the Balancing
Equation
Balancing equations such as equation (6) requires a base
population, whether estimated or enumerated, and information
on the various components of population change.
Because a principal objective of the population estimating
procedure is to uphold the integrity of the population universe,
the various inputs to the balancing equation need
to agree as much as possible with respect to geographic
scope and residential definition, and this requirement is a
major aspect of the way they are measured. A description
of the individual inputs to equation (6), which applies to
the CPS control universe, and their data sources follows.
The census base population (PCN t0). While any base
population (PCN t0, in equation [6]), whether a count or an
estimate, can be the basis of estimates and projections for
later dates, the original base population for all unadjusted
postcensal estimates and projections is the enumerated
population from the last census. For the survey controls in
this decade, Census 2000 results were not adjusted for
undercount. The census base population includes minor
revisions arising from count resolution corrections. These
corrections arise from the tabulation of data from the enumerated
population. As of May 21, 2004, count resolution
corrections incorporated in the estimates base population
Current Population Survey TP66
U.S. Bureau of Labor Statistics and U.S. Census Bureau
amounted to a gain of 2,697 people from the originally
published count. In order to apply equation (6), which is
derived from the balancing equation for the civilian noninstitutionalized
population, the resident base population
enumerated by the census must be transformed into a
base population consistent with this universe. The transformation
is given as follows:
PCN 0 = R 0 − RAF 0 − PCI 0
where R 0 = the enumerated resident population, RAF 0 =
the Armed Forces resident in the United States on the census
date, and PCI 0 = the civilian institutionalized population
residing in the United States on the census date. This
is consistent with previous notation, but with the stipulation
that t 0 = 0, since the base date is the census date, the
starting point of the series. The transformation can also
be used to adapt any postcensal estimate of resident
population to the CPS universe for use as a population
base in equation (6). In practice, this is what occurs when
the monthly CPS population controls are produced.
Births and deaths (B, D). In estimating total births and
deaths of the resident population (B and D, in equation
[6]), we assume the population universe for vital statistics
matches the population universe for the census. If we
define the vital statistics universe to be the population
subject to the natural risk of giving birth or dying and
having the event recorded by vital registration systems,
the assumption implies the match of this universe with the
census-level resident population universe. We relax this
assumption in the estimation of some characteristic detail,
and this will be discussed later in this appendix. The
numbers of births and deaths of U.S. residents are supplied
by the National Center for Health Statistics (NCHS).
These are based on reports to NCHS from individual state
and local registries; the fundamental unit of reporting is
the individual birth or death certificate. For years in which
reporting is considered final by NCHS, the birth and death
statistics are considered final; these generally cover the
period from the census until the end of the calendar year
3 years prior to the year of the CPS series. For example,
the last available final birth and death statistics available
in time for the 2004 CPS control series were for calendar
year 2001. Final birth and death data are summarized in
NCHS publications (see Martin et al., 2002, and Arias et
al., 2003). Monthly births and deaths for calendar year(s)
up to 2 years before the CPS reference dates (e.g., 2002
for 2004 controls) are based on provisional estimates by
NCHS (see Hamilton et al. and Kochanek et al., 2004). For
the year before the CPS reference date through the last
month before the CPS reference date, births and deaths
are projected based on the population by age according to
current estimates and age-specific rates of fertility and
mortality and seasonal distributions of births and deaths
observed in the preceding year.
(7)
Derivation of Independent Population Controls C–5