Decennial and Model-based Intercensal Poverty Estimates
The 1979, 1989 and 1999 poverty estimates are from the Summary File 3 (SF3)
release of U.S. Census data from the last three decades. Each poverty estimate
is for the year preceding the Census date because the survey questions ask about
income from the previous year. The SF3 files are compiled from the "long
form" Census questionnaire, which was collected from about 1 in
every six households (or about 19 million housing units in 2000). These data are
often referred to as the SF3 Census data, but it should be noted that they are
sample data with sampling error, and not a Census of the population. Poverty status
is determined for all people except institutionalized people (e.g. prisoners
or residents of nursing homes), people in military group quarters, people in college
dormitories, and unrelated individuals under 15 years old. These individuals are
excluded from both the numerator and denominator when calculating poverty rates.
They are considered neither poor nor nonpoor. For more details on the source and
accuracy of the SF3 data, see Chapter 8
of the Census Technical Documentation.
The 2010 poverty estimates, the most recent available, are based on different data
sources and are generally considered less accurate. The long form Census data provide
sufficiently large sample sizes to produce reliable poverty estimates for small
geographic units, such as the county. Census data though are only available every ten
years and therefore are unable to provide poverty estimates for intercensal years. The
U.S. Census Bureau created the Small Area
Income and Poverty Estimates program to provide more current estimates of income
and poverty. Census Bureau combines several different sources of annual data to derive
county-level poverty estimates from statistical regression models. These models relate
income and poverty to indicators based on summary data from federal income tax returns,
data on participation in the Food Stamp program, data about Supplemental Security Income
program recipiency rate, economic data from the Bureau of Economic Analysis (BEA) and the
most recent census. These estimates are then combined with direct estimates based on the
March Supplement to the American Community Survey (ACS) to provide figures which are more
precise than either set alone. The final combined estimates are referred to as
model-based. For an overview of the estimation procedure used for the small area poverty
estimates, see the Description of
Estimation Procedure, and for cautions about comparing these estimates with the
SF3-based estimates, see General
Cautions about Comparisons of Estimates.
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