Interactive State Maps FAQs
Below you will find a list of Frequently Asked Questions (FAQs)
regarding using the Interactive State Maps section of this Web site.
There are generalized questions and answers on navigating the interactive
site, and a section of questions and answers on interpreting the data.
FAQs on how to use the interactive maps site
FAQs on interpreting the interactive maps data
How to Use the Web Site
Q: After I selected new options for a map, the map
was redrawn but it still shows the data for the previous selection
criteria. Why is this?
You must click on the button labeled Show Results to draw the new
map whenever you change the selection options for Cause of Death,
Year, Gender, or Race/Ethnicity. Although changing the options does
cause the map to refresh, it does not reset to the new options until you
hit the Show Results button.
Q: How do I locate a specific county on the map?
There are several ways to locate a county. You can use the ID
tool, the county labels, or Find a County look–up tool.
Using the ID tool on the state map—First select among the options in
the dropdown boxes for Cause of Death, Year, Gender,
Race/Ethnicity, and then click the button Show Results to activate the
state map. If you know the county's approximate location on the map you
can click once inside the county boundary to activate
the ID tool and bring up a table with the county name, death rates for
racial or ethnic groups, population percentages, and county demographics.
Zooming in to view county labels—First select among the options in
the dropdown boxes for Cause of Death, Year, Gender,
Race/Ethnicity, and then click the button Show Results to activate the
state map. Make sure that the County Labels box at the lower left
corner of the display is checked to activate county names. Then use the
zoom or pan tools located at the right side of the map to zoom
in and view the counties with their names overlaid. Click the + (plus
sign)
button or one of the zoom setting buttons below it to zoom in closer and
the – (minus sign) button to zoom out. Click on the Map Mover arrows to shift the
zoomed view of the map in the direction of the arrow. Click Reset Map to
redraw the state map at the original full scale.
Using the Find a County tool on the state map—If you are unsure of
the county's location, look for the button labeled Find a County at the
bottom left corner of the display, and click once on the arrow to
activate a dropdown list of county names for the state being
displayed. Scroll down the list and click once on the
county name you wish to locate. This action will redraw the state map with the
county you selected shown within yellow highlighted borders.
Q: How do I find death rates and population
estimates about a specific county?
There are two ways to find the population estimate and age adjusted
death rate for a county:
Using the ID tool on the state map—First select among the options in
the dropdown boxes for Cause of Death, Year, Gender,
Race/Ethnicity, and then click the button Show Results to activate the
state map. The ID tool is activated when you click the mouse inside the
boundaries of a county on the map. This action will bring up a table that lists the
county name, death rates for racial and ethnic groups, population percentages,
and county demographics.
Using the ID tool on the County Listing tab—First select among the
options in the dropdown boxes for Cause of Death, Year, Gender,
Race/Ethnicity, and click the button Show Results to activate the
state map. Then select the tab labeled County Listings to bring up a
list of county names in the state being displayed in
the map. You can now click once within the borders of the
highlighted county to activate the ID tool and bring up a table that lists
the county name, death rates for the racial or ethnic groups, population
percentages, and county demographics.
Q: How do I compare my county's rates with the
state and national rates?
How to find county death rates using the ID tool
is discussed in the answer to the question: "How do I find death rates and
population estimates about a specific county?" The state and national rates for the racial
or ethnic
group selected in the mapping options are shown on the left side of the
margins of the state map. To view the national and state death rates for
other racial or ethnic groups, click on the State Statistics
tab.
Q: How do I view two maps at a time?
After selecting a state from the Heart Disease and Stroke Maps
homepage, the option to View 2 Maps appears at the upper left
corner of the screen in the block labeled CVH Contents. Clicking on
this link will bring up a new page that provides two sets of map options for
Map 1 and Map 2. For each map, click on the dropdown menu to select from
the options for Cause of Death, Year, Gender, and Race/Ethnicity
and then click on the button labeled Show Maps to draw
the maps.
Q: How do I compare maps of heart disease and
stroke for a racial or ethnic group?
Follow the instructions in the answer to the question: "How do I view
two maps at a time?" Then select heart
disease and stroke for a racial or ethnic group. Looking at the maps side
by side, you can compare disease rates for the same location (county,
state, or region) and learn whether that location has generally high,
medium, or low rates for two different diseases. Remember that the rate
maps for two different diseases are not directly comparable, since quintile
assignment is based on the distributions of county rates for each
disease. A high rate for heart disease and a high rate for stroke mean
only that the county falls at the high end of rates for each disease
compared with other counties. It does not mean that the county suffers
similar numbers of deaths for both diseases because there are many more
deaths from heart disease than stroke. For the same reason, a low rate for
heart disease and a high rate for stroke for a county does not indicate
that more people die of stroke than of heart disease in the county. To
better understand the comparative risk of each disease, you must look
closely at the map legend to note the range of death rates next to each
quintile. Rates are expressed as the average number of deaths per 100,000
people.
Additional information can be learned about the burden of two diseases for a
racial or ethnic group in a given county by comparing the county rate with
the state and national rates listed on the left side of the margins of the
state map. Assessing how county rates compare with the state and
national rates for a racial group also provides insight into
relative geographic trends of the county of interest. For example, it may
be useful to know whether the rates fall above or below the state and
national rates for each disease type.
Q: How do I compare the rates of stroke and heart
disease for two racial groups?
Follow the instructions for viewing two maps in the answer to the
question: "How do I view two maps at a time?" Then select either
heart disease or stroke for two different racial or ethnic groups. Looking
at the maps side by side allows you to see disease rates for the same
location (county, state, or region) and whether one location has
generally high, medium, or low rates for two racial or ethnic
groups. Remember that the maps for two racial groups are not
directly comparable, since quintile assignment (and map color) are based on
the independent distributions of county rates for each racial or ethnic
group. A high quintile assignment for one group and a high quintile assignment for
another group does not mean that both groups suffer similar numbers of deaths. For example, because death rates are considerably
higher for blacks than for other groups, it is common to find that the
range of death rates for the lowest quintile for blacks is comparable with
the highest quintile for whites. This substantial difference in death
rates is what public health officials refer to as a health disparity,
meaning one group has much higher disease rates than another group. To
better understand the disparity among racial groups, you must look
closely at the map legend to note the range next to each quintile.
Rates are
expressed as the average number of deaths per 100,000 people.
Additional insights about the pattern of burden of a disease
for different racial or ethnic groups in a given county can be gained by
comparing the
county rate with the state and national rates listed on the left side of
the margins of the state map. Assessing how racial or ethnic groups in the
county compare with the state and national rates for a racial or ethnic
group also provides insight into geographic health–related disparities of
the area of
interest. For example, it may be useful to know whether the rates fall
above or below the state and national rates for each racial group.
To extend the comparison further, you could also examine the death
rates for all of the racial or ethnic groups in a county by using the ID tool
to view the county statistics. With this information, you can determine
which groups have the highest and lowest death rates in a county and by
what magnitude they differ from each other. The ID table also includes the
population counts by racial group and relative frequency (percentages),
which provides information on the racial makeup of the county.
Q: Why do the map colors and map categories look different
on state maps than on
the national map?
The state maps show quintiles based on the distribution of death rates
in all counties within the state, whereas the national map shows quintiles
based on the distribution of death rates in all counties in the country.
These maps look different because there are large differences in
county death rates from state to state and region to region. The national
map shows the national disease patterns for each racial or ethnic group and
is the source for seeing how the counties in a state compare with the
counties in the rest of the country. Each state map shows the distribution
of counties with high, medium, and low rates based only on the range of death
rates within that state.
Q: How do I print a copy of a map or download a
digital version of a map to put into a report or presentation?
First select among the options for Cause of Death, Year,
Gender,
Race/Ethnicity, and then click Show Results to activate the
state map. Then click on the hyperlink labeled Print this Map in the
upper right corner of the map to create a printable image of the map
in a separate window. The image will give the user options shown in
hyperlink text at the top of the map: Send to Printer or Save
Image. The Send to Printer option sends the file to your printer.
The Save Image option produces a high resolution .jpg file suitable for
use in publications or presentations.
Q: What are the sources of the data?
The source for the mortality data used in our maps is the National
Vital Statistics System (NVSS), which is maintained by CDC's National Center for Health Statistics (NCHS).
NVSS is a compilation of statistics from all death certificates filed in
the 50 states and District of Columbia. The source for the county
population data is the U.S. Census Bureau intercensal and postcensal
population estimates. Population estimates for 2000 are Bridged
Race Census Estimates, a special dataset bridging the 31 race categories
used in Census 2000 (and afterwards), as specified in the 1997 Office of
Management and Budget (OMB) standards for the collection of data on race
and ethnicity, to the four race groups specified under the 1977 OMB
standards. These bridged data were created by the Population Estimates
Program of the U.S. Census Bureau under a collaborative agreement with NCHS to facilitate use of new population data with Vital Statistics Data
collected under the old race classifications.
How to Interpret the Data
Q: How are the spatially smoothed mortality rates
calculated?
Spatially smoothed and age adjusted death rates were calculated at the
county level, by sex, for each of the following racial and ethnic groups:
American Indians and Alaska Natives, Asians and Pacific Islanders, blacks,
Hispanics, and whites. Rates were also calculated for the total U.S.
population. For each county, the number of deaths (numerators) and
population counts (denominators) for 10 year age groups (i.e., age 35–44,
45–54, 55–64, 65–74, 75–84, and 85 or older) were
summed for the specified periods. County numerators and denominators
were then combined with numerators and denominators of all neighboring
counties. Neighboring counties were defined solely by contiguity rather
than distance. The combined numerators were divided by the combined
denominators to produce spatially smoothed, age specific (i.e., by 10–year
age group) death rates. These spatially smoothed rates were then directly
age adjusted to the 2000 U.S. standard population for the age groups 35
years or older. These calculations were repeated separately, by sex, for
each of the racial or ethnic groups. Please note: The heart
disease death rates for 1991–1995 that are published in our early atlases
were age adjusted to the 1970 U.S. standard population. However, the
online maps for 1991–1995 were updated to the 2000 standard
population.
Q: What is age adjustment?
An age adjusted mortality rate is a weighted average of age specific
rates calculated on the basis of the proportion of people in the corresponding age groups
of a standard population. Mortality rates were age adjusted to the 2000 U.S.
standard population, ages 35 years or older. Age adjustment helps to
minimize the effects of differences in age distributions across counties.
For instance, age adjustment allows the rates for a college town with a high number of young people
to be compared with the rates for
a retirement community with a lot of elderly people.
Q: Why are rates calculated for a span of years
rather than for each year?
Although heart disease is the number 1 and stroke the number 3 cause of
death in the U.S., each county has an insufficient number of deaths each
year to allow analysts to calculate reliable rates for many
non metropolitan areas with small populations and low death rates. This problem
is particularly relevant for analysts who examine geographic disparities among
racial or ethnic groups because many counties have small or no
populations of minority races. To address this constraint, deaths are
summed over 5 years for heart disease and 8 years for stroke to ensure
that stable rates can be generated by race and sex for a large number
of counties.
Q: Why are heart disease rates and stroke rates calculated for
different spans of years?
Death rates are calculated for a span of years that will allow reliable results
to be produced for minority groups and low–populated counties.
Because there are many more deaths from heart disease than from stroke, heart
disease is calculated for a 5–year span (1991–1995, 1996–2000) whereas
stroke is calculated for an 8–year span (1991–1998).
Q: Why are there no maps of death rates for
the most recent years?
It takes time (usually a year or two) for death certificate data to
make its way through several levels of
government agencies, beginning at the county courthouse and ending at
CDC's National Center for
Health Statistics, where the National Vital Statistics Database is
maintained.
Therefore, there is a lag of 2 to 3 years before data are published and available
for epidemiological studies. Adding further to the delay is the need to
calculate the disease rates of counties for a
span of years to insure reliability.
Q: What is a quintile?
A quintile is 1/5 of the distribution of all county rates. Rates
are divided into 5 equal subgroups (quintiles), ranging from
highest to lowest. Each quintile contains as near as
possible 20% of the distribution. In practical application, some quintiles in our maps do not
cover the same number of
people because some counties have the same rate, and these tied rates
may make it impossible to divide the distribution equally. The
map legend shows the ranges of death rates that define each map category
and the number of counties in each category.
Q: How do I interpret the different colors in the
map?
The colors used for each county in the map indicates which of the
five quintiles the county belongs in. The lightest hue indicates the quintile with the lowest 20% of
the death rates and the darkest hue indicates the quintile with the highest 20% of death
rates. The three middle quintiles have colors that grade between the lightest
color at the low end and the darkest color at the high end. The gray
color indicates that the county had an insufficient number of deaths or living
people to permit calculation of a reliable death rate.
Q: Why are some counties
colored gray, meaning insufficient data?
Counties were considered to have insufficient data for calculation of
a reliable death rate for a particular racial or ethnic group if the total
number of deaths in the county and its contiguous neighboring counties was fewer
than 20 during the rating period (heart disease 1991–1995 and 1996–2000; stroke 1991–1998). To avoid calculating rates for counties that
1) had nobody from a particular population living there, and 2) did have
neighboring counties with significant numbers of the population, rates
were also not calculated for counties with
a population of less than 5 during the same span of years.
Q: How do I find the rates for a city?
At present, we have only mapped only the rates for two cities: New York
City and the District of Columbia.
Q: I get different disease rates when I use my
state or county health department's health statistics Web site or the CDC
WONDER site. Why?
Differences in disease rates found through different public health sources are
probably due to
a combination of the effects of different disease rate calculation methods
and variations in population estimates.
The source for the mortality data
used in our maps is the National Vital Statistics System maintained at CDC's National Center for Health Statistics and the source for the population data is
the U.S. Census Bureau. These are the same sources used by WONDER and the
probable sources for other state or county mortality data. Generally, mortality
data are consistent from source to source. Population estimates may vary
depending on their date of acquisition, since different intercensal or
postcensal versions may have slight differences in population counts at
the county level because the US Census Bureau refigures the estimates
every few years and then revises them after the next census. These
differences in the population estimates are, even for minority groups in
low population areas, unlikely to be enough to change rates significantly.
Differences due to rate calculation methods may show more
pronounced variations in rates. The heart disease and stroke mortality
maps on this Web site are generated with rates calculated by spatial
smoothing, whereas, in general, those on WONDER and some other public health sites are
not. Smoothing was done to enhance the stability of rates
in counties with small populations. The stability of rates is particularly
at issue when analysts are examining geographic disparities among racial
or ethnic groups
because many counties have small or no populations of minority
groups.
We chose to spatially smooth death rates using a spatial smoothing
average. Death counts (numerator) and population counts (person year
denominators) for each county were combined with the deaths and population
counts of the immediate neighboring counties (i.e. contiguous counties)
and then divided to produce an average rate. Therefore a single county's
mortality rate actually represents an average of rates of that county and
all its contiguous neighbors. Rates calculated without
smoothing will have some differences from actual rates, and those
differences may
occasionally be double digit. However, there should be little difference in county rankings.
Consider the Atlases as one of several sources that provide
information about the trends in heart disease and stroke. These are not
intended to replace publications and information from local and state
health officials; rather they are supplements to these publications.
Q: Does this Web site have published reports about heart disease
and stroke that include maps?
Publication of the interactive maps on the Web site coincided with
publication of three heart disease and stroke atlases: Women
and Heart Disease (1999, 2000), Men and Heart Disease (2001), and
Atlas of
Stroke Mortality (2003). The latest publication, Atlas of Heart Disease
and Stroke Among American Indians and Alaska Natives (2005) incorporated
the most recent county data on heart disease and stroke along with
state data on risk factors from the Behavioral Risk Factor Surveillance
System. These publications are available
from this Web site in electronic PDF format, or they can be
ordered in hardcopy form (while supplies last) from CDC at the link below:
Go to the page for downloading the atlases in PDF format:
http://www.cdc.gov/hdsp/library/other_publications.htm
Go to the page to order the hardcopy atlases:
http://www.cdc.gov/hdsp/library/atlas-order.htm
Q: How do I cite the Web site data?
A suggested citation for the Web site publication is included on the map image when
the print/download tool is used. It reads: Centers for Disease Control and
Prevention, Heart Disease and Stroke Maps
[online]. 2005. [accessed (todays date)]. URL:http//www.cdc.gov/hdsp/library/maps/index.htm
Back to top
Date last reviewed:
05/12/2006
Content source: Division for Heart Disease and Stroke
Prevention,
National Center for Chronic Disease Prevention and
Health Promotion
|
