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E-2. California County Population Estimates and Components of Change by Year — July 1, 2000–2006

December 2006

OFFICIAL STATE ESTIMATES

Acknowledgments

Linda Gage produced the state and county estimates and prepared this report.  Mary Heim contributed expert consultation and insights into the estimating methods and data sets.  Melanie Martindale produced the birth projections.  Douglas Kuczynski collected and prepared the group quarters data.  Evaon Schnagl produced the school enrollment projections and prepared the driver's license address change data.  Daniel Sheya validated input data, formulas and methodologies used in the current state and county estimates series.

Suggested Citation

State of California, Department of Finance, California County Population Estimates and Components of Change by Year, July 1, 2000-2006. Sacramento, California, December 2006.

• Press Release (.doc)
• E-2. California County Population Estimates and Components of Change by Year — July 1, 2000–2006 (.xls, 136k)

Contents

This report presents provisional state and county population estimates for July 1, 2006; revised estimates for July 1, 2000 through July 1, 2005; and components of population change by year between fiscal years 1999-00 and 2005-06

Highlights

California’s population grew to 37,444,000 on July 1, 2006, according to official population estimates released today by the State Department of Finance.  The growth of 1.25 percent, representing 462,000 new residents during the fiscal year, continued the pattern of slower growth rates each year since the 2.0-percent growth in 2000.

The balance of 552,000 births and 235,000 deaths resulted in a natural increase of 317,000 persons.  This accounted for 68.5 percent of the 2006 fiscal year growth.  Natural increase remains an increasing source of the state’s growth this decade.  Net migration contributed over 146,000 new residents, 31.5 percent of the growth.  This estimate includes all legal and unauthorized foreign immigrants, residents who left the state to live abroad, and the balance of hundreds of thousands of people moving to and from California from within the United States.  During the fiscal year, the state gained over 213,000 new foreign immigrants and, similar to last year, experienced a modest loss of 67,000 persons to other states.

Since July 2000, the state has grown by 3.3 million persons for an overall growth rate of 9.8 percent.  There have been 3.2 million births, 1.4 million deaths for a six-year natural increase of 1.8 million added to 1.4 million foreign immigrants and 105,000 domestic migrants.

Methodology

The state and county populations are independently estimated using population change models benchmarked on official decennial census counts. The state population is estimated using the Driver License Address Change method. County population proportions are estimated using the average of three separately estimated sets of proportions. The final distribution of proportions is applied to the independently estimated state control.

State. The state population is estimated using the Driver License Address Change (DLAC) method. This composite method separately estimates three population age groups:  under 18, 18 through 64, and 65 and over.  The estimate of the youngest group employs a survived census cohort, births, deaths, public school enrollment in grades one through eight, and enrollment to census ratios.  The estimate of the 18-64 group relies on a survived census cohort, migration estimates based on driver license address changes and federal tax return data, immigration estimates based on data from the U.S. Citizenship and Immigration Services, Office of Immigration Statistics, and death data.  The estimate of the oldest group is based on changes in Medicare and Medi-Cal enrollments.  Population in college dormitories, state and federal institutions, military barracks, and other group quarters are added to over 18 population groups.

Counties. County population proportions result from averaging three methods.

DLAC Method. A modified version of the State Driver License Address Change method is used for counties.  County proportions of the State total result from changes in county population values for births, deaths, school enrollment, foreign and domestic migration, medical aid enrollments and group quarters population.

Ratio-Correlation Method. This method models change in household population as a function of changes in the distributions of driver licenses, school enrollments, housing units, and deaths.  Estimates of county group quarters are added.

Tax Return Method. County proportions are derived by the U.S. Census Bureau using matched federal income tax returns to estimate intercounty migration along with vital statistics, group quarters and other information for the population aged 65 and over.

Data Considerations

Sources. Data used in estimation models come from administrative records of 17 state and federal departments and agencies.  Timeliness and coverage in these series vary.  Corrections, adjustments or estimates may be made while preparing the estimates.

Accuracy. Data and models used to produce population estimates are subject to both measurement and nonmeasurement errors.  This results in imperfect correlations between the data used to estimate the population and actual population change.  The data and estimating models have been thoroughly tested with decennial census results that provide benchmarks for the estimates series.  Compared to the 2000 decennial census counts for California's counties, results of the estimation models differed by an average of 1.9 percent. The total state estimate was within one-half of one percent (0.5%) of the decennial census count.  Data and methods are further refined and modified throughout the decade.