Department of Finance
915 L Street
Sacramento, CA 95814
July 2007
Acknowledgments
Mary Heim and Melanie Martindale prepared this population projection series. Programming expertise was furnished by Iris Wang.
Suggested Citation
State of California, Department of Finance, Population Projections for California and Its Counties 2000-2050, Sacramento, California, July 2007.
See 'Viewing
Documents' for information on accessing
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Data Sources
The California Department of Health Services provided the vital statistics (births and deaths) used in this projection series. In response to a 2006 survey, planning experts of several counties and Councils of Government contributed assessments of future migration and population for their jurisdictions.
Authority
These population projections were prepared under the mandate of Government Code, Sections 13073 and 13073.5. In addition, the State Administrative Manual, Section 1100 on state plans, sets the general policy of . . . "(3) The use of the same population projections and demographic data that is provided by the State’s Demographic Research Unit.
Technical Notes
Basic Method
The Department of Finance uses a baseline
cohort-component method to project population
by age, gender and race/ethnicity. For this
projection series, there are seven mutually
exclusive race/ethnic groups: Hispanics and
non-Hispanic American Indians, Asians, Blacks, Multirace persons, Pacific Islanders
and Whites. A baseline projection assumes people have the right to migrate
where they choose and no major natural catastrophes or war will befall the
state or the nation. A cohort-component method traces people born in a given
year through their lives. As each year passes, cohorts change as specified
in the mortality and migration assumptions. New cohorts are formed by
applying the fertility assumptions to women of childbearing age.
Special
Populations
Special (institutionalized)
populations are populations that do not age
normally. They
are found primarily in prisons, college dorms,
and group housing on military installations. These
populations tend to remain static in age as
people enter and leave the institutions. In
counties where special populations represent
a significant proportion of a specific race/ethnic
group's population, they were removed from
the base and projected separately. For
prison and military populations, the determination
was made based on an examination of sex ratios. Adjustments
to college dorm populations were based on an
examination of age structure. Forecasts
from the Department of Corrections and Rehabilitation
and the various college campuses were used
to determine the opening/closing of facilities.
Survival, Fertility and Migration Proportions
Survival Rates
For the starting date, state-level survival rates were constructed separately
for men and women of seven race/ethnic groups. That is, life tables were
created for men and women of each race/ethnic group using a five-year average
of death data (CY 2000-2004), with the survival rates being derived from each
of these life tables.
Fertility Rates
A set of six 5-year age-specific fertility
rates (ASFRs for the age range 15-44) for
each of seven race/ethnic groups was calculated
for each county for each year of the period
2000-2004. For the numerators of
these rates, births to mothers under age
15 and births to mothers of unknown age
were added to the births of the youngest
age group and births to mothers over age
44 were added to births of the oldest age
group. Rate denominators were published
E-3 2000-2004 estimates by age, gender
and race/ethnic group for each county. ASFRs
were then averaged for each race/ethnic
group of each county to derive beginning
fertility rates for the projections. In
San Luis Obispo and Yolo counties adjustments
to the E-3 populations were made for college
students.
Migration Proportions
Migration proportions were developed for
the decade of the 1990s by a survived population
method. The 1990 population was aged
forward in time to 2000 by adding recorded
births to form new cohorts and subtracting
deaths from existing cohorts. The survived
1990 population was compared to the 2000
population and differences were assumed to
be migration. The ten-year migration was
annualized and divided by the total to derive
a proportion. Then a three-year moving
average was used to smooth the migration
proportions.
Assumptions
Base Population: As the benchmark (or starting population), the Department of Finance has used the 2000 Census counts as modified by the Bureau of the Census to eliminate the “Other” race category. These counts represent a modification to the race distribution of the census count and not an adjustment for undercount to the total.
Fertility: Two fertility options were used. Depending on current levels and historical trends, local area fertility was either merged to the state norm or followed the state trends. The state fertility norms as expressed in terms of total fertility are as follows:
Mortality: Evaluation of the life tables by county, gender and race/ethnic group revealed that the county tables contained many small data cells that could not deliver consistent results. Therefore, statewide survival rates by gender and race/ethnic group were used for all California counties. State-level survival rates were merged to 2050 national-level race/ethnic- and gender-specific survival rates published by the US Census Bureau. It was assumed that the higher of the state rate or the national rate for each race/ethnic-, age- and gender-specific group would be used as the group's 2050 survival rate. The implied life expectancies by race/ethnic group and gender were:
Migration: The Department of Finance relied on the expertise of local agencies to assist in the development of local area migration assumptions. When local input was not available, the migration assumptions were made by the Department of Finance based on historical analysis of the county’s migration patterns. On a statewide basis, net migration averages 177,000 over the 50-year period.
Demographic Model
The benchmark population was projected using the fertility, mortality and migration assumptions. Applying the fertility assumptions to the women of childbearing ages creates new cohorts. The population ages with time, as the gender-, race/ethnic-, and age-specific survival rates are applied to the population at risk. In addition, the overall migration assumptions by race/ethnicity are distributed using the assumed gender and age proportions. The process is carried forward for 50 years from 2000. Special populations are then added to produce total population projections.