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AGS Estimates 2009 & Projections 2014
Estimates and Projections - Methodology
The Estimates and Projections (E&P) database is the most extensive
update available, covering a broad range of demographic characteristics
for the current year, and 5- and 10- year projections. Variables include:
• Population
• Population by household type (family, non-family, group quarters)
• Households
• Households by type (family, non-family)
• Households by size of household
• Households by age of head of household
• Household type (e.g. lone parent male family with children)
• Average Household Size
• Population by age (19 age breaks)
• Population by age and sex (38 breaks)
• Population by sex
• Population by race
• Population by Hispanic origin
• Population by race and Hispanic origin (e.g. white-Hispanic,
white non-Hispanic)
• Hispanic origin by nationality (e.g. Mexican, Cuban)
• Population by Marital Status
• Population by Educational Achievement
• Labor Force Employment Status
• Labor Force Occupation
• Labor Force Industry
• Aggregate Income (family, non-family households, group quarters)
• Household income distribution (15 breaks)
• Family income distribution (15 breaks)
• Extended Upper-Income distributions
• Median and average income (family, household)
• Disposable income distribution
• Age of head of household by income
• Vacant Dwellings
• Tenure
• Vehicles Available, Total and by number per household
Methodology and Data Sources
AGS uses a wide range of data sources in constructing its estimates and projections, including:
(1) Census Bureau estimates and projections of population characteristics at various levels of geographic detail, including the latest estimates of population at the city level
(2) Bureau of Labor Statistics estimates and projections of employment by industry and occupation at the county level
(3) Medicare eligible population counts at the ZIP code level, including population by sex and 5-year age cohorts, provided by the Health Care Financing Administration of Social Security. These counts provide a very accurate local count of the population aged 65 and higher.
(4) Internal Revenue Service statistics on tax filers and year-to-year migration
(5) The Census Bureau's Current Population Survey, which provides detailed demographic breakdowns and enables a thorough longitudinal analysis of demographic trends
(6) Experian's INSOURCE database, a household level credit and demographic database which covers the vast majority of households
INSOURCE is a vast database at the household and individual level that
Experian provides to AGS for use in its demographic estimates. The INSOURCE
database was aggregated to the ZIP+4 and Block Group levels of geography
for analysis and standardized to Census Bureau county level current estimates.
A large number of demographic attributes from INSOURCE were utilized in
building the 2000 estimates, including:
• Population
• Population by Age
• Households
• Household Size
• Household Type (presence of children)
• Marital Status
• Income
• Hispanic origin
• Population of Asian origin
• Dwelling Tenure (own/rent)
In turn, the AGS demographic estimates are used as the foundation of Experian's U.S. MOSAIC segmentation system.
Now in its third year of use within the AGS estimates methodology, INSOURCE provides an excellent source of small area year-to-year change which greatly improves the quality of local estimates, especially in areas of growth.
The estimates and projections methodology combines the best current and projected information from the data sources noted above. It is supplemented by the extensive experience of Applied Geographic Solutions in creating accurate and reliable estimates and projections. A summary of the methodology for each of the major variable groups is included in the sections that follow.
Population
The current population of the United States is obtained from the monthly Census population estimate. This is a very accurate and current estimate of the population and serves as the basis for projection and estimation at lower levels of geographic detail. The five and ten year projections have been derived from the middle-series projections of the Census Bureau.
State and county level estimates are based on the compilation of data from a range of Federal and State authorities, including the latest county population estimates from the Census Bureau, reviews of building permit statistics, the current population survey (CPS), and additional local sources. Where required, the resulting estimates are then ratio-adjusted so that the sum of the county estimates is equal to the state total, and the state estimates equal to the national total. For the five- and ten-year projections, a similar method is employed. However, rather than using simple straight-line techniques, AGS uses straight-line methods only for growing areas. For declining areas, a log-normal extrapolation is used. This has the effect of slowing decline over time, which is characteristic of long-term population decline at the state level.
At the block group level, the population model consists of the application of a non-linear trend model which estimates population given historical patterns, INSOURCE population counts, and the latest Census age distributions (using cohort-survival techniques). Special consideration is given to the population age 65+ by applying ZIP code level counts by age and sex of all Medicare eligible persons. This provides considerable improvement in the estimates of this important segment of the population. The final results are then carefully balanced to the county and city level population estimates to ensure consistency with current Census Bureau estimates.
The result is a comprehensive set of population estimates and projections which includes the knowledge of State, County, and private agencies about their detailed areas but also ensures that the total population is consistent with the Census Bureau estimates, which have proved extremely reliable over time.
Population By Age, Sex, and Race
National and State level Census bureau projections of age by sex and race/Hispanic origin were used as overall controls to ensure consistency with the Census projections. Detailed forecasts by age, sex, and race, as well as Hispanic origin, were obtained from the Census Bureau 'middle series' projections.
It the state level, the projections of individual state agencies were combined with the results of a cohort survival approach to obtain reliable state estimates by age and sex. The block group estimates were compiled using cohort survival methods, then balanced to both the estimated block group population totals and to the state level control totals. Consistency checks with the annual CPS (Current Population Survey) are used to ensure the validity of the resulting age/sex distributions. Further, INSOURCE population by age summaries were used to adjust local estimates for the adult population, with further adjustments applied using the ZIP code level Medicare eligibility statistics.
Trends in the racial distribution and Hispanic populations were used to derive preliminary estimates at the block group level, which were then adjusted to balance with appropriate control totals. This method allows the utilization of the historical changes in race and Hispanic origin distributions and projects those changes into the future while maintaining consistency with national level projections. Again, the CPS is used extensively to assist in the verification of the models.
Households and Household Type
Total households were modeled by:
-projecting trends in the population per household over time at the national level to provide a control total;
-reviewing currently available household size statistics at the State level; and utilizing the current estimates of population by age and sex to determine household formation rates for small areas
All household based numbers are initially estimated / projected separately for family and non-family households. Non-family households have been growing in number at a higher rate than family households have over the past several decades. Average household sizes for family households have been decreasing for several decades. However, during the 1990's, the decline has stopped in most areas and has actually reversed in several states.
The group quarters population, that is population that is not in households (such as persons in institutions, military barracks, nursing homes, college dormitories, and homeless persons), is expected to increase slightly during the decade, but remain relatively constant as a percentage of the total population. This is a reflection of two trends: the decreasing armed forces employment since the 1980's and the longer term increasing elderly population which results in high populations in nursing homes and other institutions which cater to the elderly population. As a result, the total group quarters population has been relatively constant.
Income
Income estimates include aggregate income by household type and income distributions as well as derived measures include per capita income, and various median income measures.
All income estimates produced by Applied Geographic Solutions are in current, rather than constant, dollars. In other words, a projection of income for the year 2010 includes both an inflationary component and a 'real' component, the latter being the difference between the change in income and the change in inflation during the period. The 'real' component is normally attributed to productivity gains in the economy and to differences in the international competitiveness of the economy.
Aggregate income estimates for the current year are based on an analysis of changes in per capita income between the 1990 Census and the most recently available income statistics (Census Bureau and IRS) at the national, state, and county levels. The projections of aggregate income are based on a review of Bureau of Economic Analysis (BEA) projections, which assume an effective increase of 3.5% per annum in per capita incomes during the next ten years at the national level.
Income distributions are estimated and projected for both family households and non-family households separately. Total household income distributions are simply the aggregate of the two detailed distributions.
Income distributions were derived by using a complex distribution shifting technique which utilizes the changes in per family household and non-family household incomes as a means of adjusting the income distributions over time. The relative ratio between changes in per household average incomes and median incomes were used to adjust for above-average growth in high-income households within some geographic areas. The resulting distributions were then normalized to higher order totals and adjusted to national level expectations and were verified for internal consistency with respect to the mean and median measures.
For the 2000 year estimates, a new set of income breaks are provided for the $150,000+ category, namely $150000-$199999, $200000-$249999, $250000-$349999, $350000-$499999, and $500000+. Created by using logistic regression techniques that account for the local income distribution, these should be considered as maximum likelihood estimates. Although little data exists to substantiate incomes in these ranges, comparisons have been made to IRS taxation statistics to ensure that the results are consistent. Users are cautioned that these estimates are statistical in nature only.
Employment Characteristics
Current employment characteristics are available from a range of sources covering unemployment rates, labor force participation rates, and occupations. The primary information sources are the Bureau of Labor statistics and the Census Bureau.
Projections are based on a set of county level projections compiled by the Bureau of Labor Statistics, using the "moderate growth" series. It should be noted that there are substantial differences in the population estimates and projections between the BLS and Census estimates. The BLS numbers were therefore used as an allocation guide rather than in absolute form, as the Census estimates are generally considered more reliable.
Below the county level, 1990 Census breakdowns were used as a base for simultaneously adjusting to the new labor force totals at the block level and the updated industry/occupation breakdowns at the county level. The method used is a maximum entropy matrix balance, which ensures that the new totals will be met with minimal change to the overall structure of the original detailed matrix. In simple terms, it adjusts the values as little as possible to ensure that the new totals are reflected.
Other Variables
A number of other variables are also projected within the series. In large part, these are derived by using available current estimates and projections at the lowest possible level of geography as the base for the estimation procedures. The CPS is used extensively to track changes using available cross-reference information related to age, race, sex, and income. Where possible, these CPS statistics are supplemented by INSOURCE estimates.
For example, current marital status estimates are available at the state level from the Census Bureau as "control targets". The CPS surveys (both historical and current) are used to track the changes in marital status dependent upon other symptomatic variables such as age, sex, race, and income levels. These "micro-models" are then applied to the block group level changes between the census and the current period. This results in block group level data which is consistent with higher order levels but also reflects changes in marital status owing to shifting local demography.
On the other hand, vacant housing is tracked using state and regional indicators, then adjusted for seasonally vacant dwellings which are a significant component of the marketing landscape in many areas of the country.
