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Data Guidelines |
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Guidelines for Using Rural-Urban Classification Systems
for Public Health Assessment
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Trend analysis
Four major changes occurred between the 1990 and 2000 US
Censuses which complicate attempts to track trends in
rural-urban disparities.
1) Census tract boundaries were realigned. An overlay of
1990 and 2000 Washington Census Tracts (Appendix 3)
shows that the realignments are particularly noticeable
in the rapidly growing areas surrounding major
population centers.
2) As discussed in
What Systems are commonly used to
classify the rural urban character?, the US Census
Bureau revised the methodology for establishing
Urbanized Areas and Urban Clusters in 2002. These
changes expanded the boundaries of Urbanized Areas.
Figure 1 compares 1990 and 2000 Census Urbanized Areas
in Washington. It is unclear how much of the change
between 1990 and 2000 is the result of the new method
and how much is due to population growth, because the
new method has not been applied to 1990 data. Because
most rural classification schemes use the Urbanized Area
definition as a starting point, this change has had
broad ramifications. Chief among them is that
comparisons over time are difficult to interpret.
3) As described in
Washington State classifications by
county, the US Census Bureau revised the methods for
establishing Metropolitan and Non-Metropolitan areas in
2003 This change also affected Urban Influence Codes and RUCC which are tied to the Metropolitan definitions.
4) The rules for classifying census tracts for RUCA
codes were revised in 2005. The primary change was
raising the lower threshold for establishing commuting
relationships from 5% to 10%. The primary effect of this
change was to increase populations and areas classified
as rural.
Rural-urban trends between 1990 and 2000 are obscured
due to the magnitude and complexity of these changes and
the absence of bridging methods built on 1990 and 2000
US Censuses.
Recommendations for
trend analysis-
Because classification systems built on the 1990 and
2000 US Censuses are not comparable, the
DOH Community
Health Systems Office recommends beginning trend
analysis in 1995 and using classification systems based
on methods that incorporate 2000 US Census data.
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The author should note that the comparison is based on
classifications at a point in time (2000). Some areas,
particularly those with large population change, may be
misclassified or would change classification if more
complete data were available. An assessment of
population change within classifications across the
study years might help interpret findings.
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If the data analyst needs to assess trends prior to
1995 using systems based on 1990 and 2000 US Censuses,
we recommend that the analyst
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Explore the significance of classification changes
before treating the data as a continuous series.
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Clearly show on trend lines or charts where major
methodological changes occurred.
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Interpret trends with caution.
Other considerations when making rural-urban comparisons
in Washington
Because the proportion of elderly residents in rural
areas is higher than in urban areas, the analyst should
consider age-adjustment for age-related public health
indicators. (See
Rates guideline for a discussion of
age-adjustment.) Analysts should also keep in mind that,
in general, the residents of rural Washington have lower
incomes, have completed fewer years of formal education,
and have differing racial and ethnic backgrounds than
those in other areas. Differences in health status
between rural and urban Washingtonians may reflect these
underlying differences in demographics.
There are also regional variations in the demographic
structure of rural Washington. The Hispanic population
has a strong presence in Central Washington, and the
tribal population has a strong presence in Northeast
Washington. Northwest Washington (San Juan and Island
Counties) are more Caucasian and affluent.
Walla Walla, Whitman, and Kittitas Counties host
universities which have significant influences on both
age and poverty structure. Island County has a very
large military presence. Sensitivity analyses excluding
these “outlier” counties may be warranted in analyses
examining health indicators or population demographics
that may be inordinately influenced by these
populations.
Guidelines: A recap
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When making rural-urban comparisons definitions
matter. It is essential that analysts document the
classification system, including explaining why the
system was selected, and discussing its strengths,
limitations and possible biases. This information needs
to be easily accessible to users to help them interpret
findings and compare across studies.
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If data are available at the census tract or ZIP code
level, use the RUCA system, collapsing the ten RUCA
codes into four categories as in
Table 3.
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If data are only available at the county level, use
Metropolitan, Micropolitan and Outside Core-Based
Statistical Area classifications.
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Changes over time may be best assessed using 2000
rural-urban designations and 1995 as a starting point.
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Trend analyses using classification systems built on
the 1990 and 2000 US Censuses are not recommended
because of methodological changes and the absence of
bridging data between census years. If long term
comparisons are attempted,
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County-level classifications are more stable than
those based on smaller geographies.
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Bias due to changes in methods and geographic
boundaries needs to be discussed.
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Rural-urban health differences may reflect underlying
differences in demographics. In general, rural-urban
comparisons of public health indicators should be
age-adjusted, as the proportion of elderly residents in
rural areas is higher than in urban areas. Analysts
should also keep in mind that, in general, the residents
of rural Washington have lower incomes, have completed
fewer years of formal education, and have differing
racial and ethnic backgrounds than those in other areas.
Acronyms
| DOH |
Washington State Department of Health |
| OFM |
Washington State Office of Financial
Management |
| OMB |
US Office of Management and Budget |
| RUCA |
Rural-Urban Commuting Areas |
| RUCC |
Rural-Urban Continuum Codes |
| USDA |
US Department of Agriculture |
| WWAMI |
Washington, Wyoming, Alaska, Montana, and
Idaho |
References
Hart LG, Larson E, and Lishner GM. Rural definitions for
health policy and research. American Journal of Public
Health; 95:7, 2005 July, pp 1149-115
Ricketts TC, Johnson-Webb KD, Taylor P. Rural
definitions for health policy makers. Bethesda (MD):
Dept. of Health and Human Services (US), Federal Office
of Rural Health Policy; 1998 July.
Appendix 1: Comparison of public health indicators
using 2001 and 2008 four-tiered consolidations of RUCA
codes
Comparison of public health indicators using
four-tiered consolidations of Rural Urban Commuting Area
(RUCA) codes recommended in the 2001 and 2008 versions
of the Washington State Department of Health's
Guidelines for Using Rural-Urban Classification Systems
for Public Health Assessment.
|
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2001 four-tiered RUCA consolidation |
2008 four-tiered RUCA consolidation |
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Indicator |
Urban Core
% (CI)* |
Sub-Urban
%(CI) |
Large Rural
Town
%(CI) |
Small
Town/Isolated
Rural %(CI) |
Urban Core
%(CI)* |
Sub-Urban
%(CI) |
Large Rural
Town
%(CI) |
Small
Town/Isolated
Rural %(CI) |
|
Percent of adults ages 18 and over
who report having health insurance,
2004-2006 |
83 (+ <1) |
83 (+ 2) |
80 (+ 2) |
73 (+ 2) |
83 (+ <1) |
83 (+ 1) |
80 (+ 2) |
73 (+ 2) |
|
Percent of adults ages 18 and over
who report a usual source of health
care, 2004-2006 |
78 (+ <1) |
80 (+ 1) |
78 (+ 1) |
75 (+ 1) |
78 (+ <1) |
80 (+ 1) |
78 (+ 1) |
75 (+ 1) |
|
Percent of adults age 18 and over
who report ever having a heart
attack, angina, or coronary heart
disease, 2004&2006 |
5.4 (+ <1) |
6.1 (+ <1) |
5.6 (+ <1) |
6.4 (+ <1) |
5.4 (+ <1) |
6.1 (+ <1) |
5.5 (+ <1) |
6.4 (+ <1) |
|
Percent of women age 50 and over
who report breast cancer screening,
2004&2006 |
80 (+ 1) |
77 (+ 3) |
81 (+ 2) |
74 (+ 2) |
80 (+ 1) |
77 (+ 3) |
81 (+ 2) |
74 (+ 2) |
|
Percent of adults age 50 and over
who report colorectal cancer
screening, 2004&2006 |
63 (+ 1) |
61 (+ 2) |
57 (+ 2) |
58 (+ 2) |
63 (+ 1) |
61 (+ 2) |
57 (+ 2) |
58 (+ 2) |
|
Percent of women age 18 and over
who report cervical cancer
screening, 2004&2006 |
79 (+ <1) |
78 (+ 2) |
78 (+ 2) |
76 (+ 2) |
79 (+ <1) |
78 (+ 2) |
78 (+ 2) |
76 (+ 2) |
|
Percent of adults age 18 and over
who report having visited a dentist
in past year, 2004&2006 |
73 (+ <1) |
69 (+ 2) |
66 (+ 2) |
65 (+ 2) |
73 (+ <1) |
69 (+ 2) |
66 (+ 2) |
65 (+ 2) |
|
* Age-adjusted percent
Source: Washington State Department of Health,
BRFSS Dataset, compiled by Washington State
Department of Health Community Health Systems
Office |
Appendix 2: RUCA code definitions
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Rural-Urban
Commuting Area (RUCA) Code Definitions: Version
2.0 |
|
1 Metropolitan area core: primary flow within an
urbanized area |
7 Small rural town core: primary flow within an
Urban Cluster of |
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(UA) |
2,500 to 9,999 (small UC) |
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1.0 No additional code |
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7.0 No additional code |
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1.1 Secondary flow 30% to 49% to a larger UA |
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7.1 Secondary flow 30% to 49% to a UA |
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7.2 Secondary flow 30% to 49% to a large UC |
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2 Metropolitan area high commuting: primary flow
30% or more |
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7.3 Secondary flow 10% to 29% to a UA |
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to a UA |
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7.4 Secondary flow 10% to 29% to a large UC |
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2.0 No additional code |
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2.1 Secondary flow 30% to 49% to a larger UA |
8 Small rural town high commuting: primary flow
30% or more |
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to a small UC |
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3 Metropolitan area low commuting: primary flow
10% to 30% to |
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8.0 No additional code |
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a UA |
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8.1 Secondary flow 30% to 49% to a UA |
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3.0 No additional code |
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8.2 Secondary flow 30% to 49% to a large UC |
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8.3 Secondary flow 10% to 29% to a UA |
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4 Micropolitan area core: primary flow within an
Urban Cluster |
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8.4 Secondary flow 10% to 29% to a large UC |
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of 10,000 to 49,999 (large UC) |
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4.0 No additional code |
9 Small rural town low commuting: primary flow
10% to 30% to |
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4.1 Secondary flow 30% to 49% to a UA |
a small UC |
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4.2 Secondary flow 10% to 29% to a UA |
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9.0 No additional code |
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9.1 Secondary flow 10% to 29% to a UA |
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5 Micropolitan high commuting: primary flow 30%
or more to a |
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9.2 Secondary flow 10% to 29% to a large UC |
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large UC |
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5.0 No additional code |
10 Isolated small rural areas: primary flow to a
tract outside a |
|
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5.1 Secondary flow 30% to 49% to a UA |
UA or UC |
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5.2 Secondary flow 10% to 29% to a UA |
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10.0 No additional code |
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10.1 Secondary flow 30% to 49% to a UA |
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6 Micropolitan low commuting: primary flow 10%
to 30% to a |
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10.2 Secondary flow 30% to 49% to a large UC |
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large UC |
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10.3 Secondary flow 30% to 49% to a small UC |
|
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6.0 No additional code |
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10.4 Secondary flow 10% to 29% to a UA |
|
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6.1 Secondary flow 10% to 29% to a UA |
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10.5 Secondary flow 10% to 29% to a large UC |
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10.6 Secondary flow 10% to 29% to a small UC |
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UA = Urbanized Area UC = Urban Cluster |
Source:
University of Washington WWAMI Rural Research
Center |
Appendix 3: Comparison of the 1990 and 2000 census tract
boundaries
(Click map for larger image)
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