Methodology

Population Estimation and Projection

The current population of the United States is obtained from the monthly Census Bureau 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 year projections have been derived from the middle-series projections of the Census Bureau.

The current year estimates rely heavily on the 2000 Census block level population counts, as these provide the most accurate recent data available. These 2000 Census counts replace the 1990 Census counts as the basis for undertaking estimates. In effect, the latest Census tabulation provides a baseline for the estimates and projections.

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, the American Community Survey, 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.

AGS CY Estimates and Projections - Data Sources

AGS uses a wide range of data sources in constructing its estimates and projections, including:

• Census Bureau tabulations from 1970, 1980, 1990 and most recently, the release of the 2000 Census
• Census Bureau estimates and projections of population characteristics at various levels of geographic detail, including the latest estimates of population at the city level.
• The Census Bureau's American Community Survey results, which cover over 60% of the national population and serve as an increasingly important attribute base at the county, metro, and state levels.
• USPS and commercial source ZIP+4 level delivery statistics
• Bureau of Labor Statistics estimates and projections of employment by industry and occupation at the county level
• 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.
• Internal Revenue Service statistics on tax filers and year-to-year migration.
• Census Bureau's Current Populations Survey (CPS), which provides detailed demographic breakdowns and enables a thorough longitudinal analysis of demographic trends
• Experian's INSOURCE, 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 current year 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)
• Length of Residence

In turn, the AGS demographic estimates are used as the foundation of Experian's U.S. MOSAIC segmentation system.

Now in its seventh 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.

Consumer Expenditure - Data Sources and Methodology

The consumer expenditure database consists of a multi-level hierarchical classification of household expenditures, which covers the majority of annual household expenditures. It is derived from an extensive modeling effort using the 2001-2002 Consumer Expenditure Survey data from the Bureau of Labor Statistics. The BLS survey is a comprehensive survey that averages over 5,000 households four times a year using a rotating sampling frame. The use of several consecutive years of data provides a rich base of expenditure data from which to build expenditure models based on household demographics.

The database consists of a total of 493 base variables, which are aggregated in up to four levels of detail. A hierarchical structure is utilized throughout, so that it is possible to aggregate or disaggregate categories as required for analysis.

The survey includes a wide range of demographic attributes related to "consuming units" (generally households), which have been modeled separately for each discrete expenditure category. The older surveys were first inflated to the current price levels using the detailed consumer price index series. For each individual expenditure category in the survey, summary statistics were calculated for each separate element in the list below. In several cases, it was possible to utilize cross tabulation data (e.g. income by age of head of household). These variables are listed below:

• geographic region (Northeast, South, Midwest, West)
• metropolitan status (metropolitan, non-metropolitan) and size (e.g. > 4 million)
• housing tenure (owner or renter)
• age of head of household (<25 years, 25-34 years, 35-44 years, 45-54 years, 55-64 years, 65-74 years, and 75+ years)
• size of household (1 person, 2 persons, 3 persons, 4 persons, 5 persons, 6+ persons)
• household income (<5000, 5-10000, 10-15000, 15-20000, 20-30000, 30-40000, 40-50000, 50-70000, 70000+)
• race (White, Black, American Indian, Asian)
• number of vehicles (none, 1, 2+ vehicles per household)

The total sample was utilized to obtain an average expenditure for each item. For each expenditure item, a series of adjustment factors were derived for each unique demographic attribute. These adjustment factors were then applied to the block group level using the same demographic variables in order to create estimates at the local level, which are consistent with local characteristics. Consistency checks were undertaken in order to ensure that the results at the block group level were consistent in the aggregate with overall income levels and published expenditures. Finally, the 2001-2002 estimates were inflated using detailed consumer price indexes to current levels.

In total, there are 393 detail categories that can be aggregated using the field name. The field name will in all cases begin with the four-character sequence X00 in order to distinguish these variables from those of other databases and from other years. The next two characters are the major group (e.g. AP for apparel). The primary detail level is a one-digit number (e.g. AP1 is men's apparel). Two sequences of two digits then follow to indicate the remaining two levels of potential detail. The entire variable list is included in the file layout section.

In addition to providing average household expenditures, AGS also provides total market estimates for use in market share and demand analysis.

Crime Statistics

CrimeRisk, from AGS, is the result of an extensive analysis of over seven years of FBI crime statistics. Based on detailed modeling of the relationships between crime and demographics, CrimeRisk provides an accurate view of the relative risk of specific crime types at the block group level. The AGS Crime database provides indexed crime data for your geography. It provides indexes for assault, burglary, larceny, motor vehicle theft, murder, personal crime, property crime, rape and robbery. It also provides an index for total crime in the area.