About Population Data

about population data

The Tracking Network includes data on population characteristics to:

  • generate rates with other data available on the Tracking Network,
  • better understand the factors that influence environmental exposures and human health in Iowa, and
  • track the impact of public health policies aimed at lessening the environmental burden on various populations.

This page provides general information about population data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.

Information on this page:

What do these data tell us?

  • The numbers of people and their location.
  • The characteristics of the population by age, gender, race, and ethnicity.

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How we can use these data?

  • These data provide the best estimate for population size and for providing data needed to produce age, gender, and race adjusted rates.
  • The number of people in a county or state provide the baseline of people that could potentially display acute and chronic illnesses and that could be exposed to different chemicals in the environment.
  • The number of people is useful in calculating the amount of resources needed for a public health response or for public safety.
  • The characteristics of the population, specifically age, gender, race, and ethnicity provide information about the variation of the population, which in turn can lead to hypotheses about the types and rates of disease and exposures.

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What can these data not tell us?

  • These data may not accurately capture certain populations that are highly transient, meaning they move frequently within and between jurisdictions.
  • Individual risk factors beyond age, sex, race, and ethnicity are not accounted for in these data.

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What is the source of the data?

  • The National Center for Health Statistics (NCHS) releases bridged-race estimates by single-year of age at the county level to allow public health agencies and researchers create and evaluate measures and rates. These estimates are derived from the U.S. Census Bureau unbridged population estimates for five-year age groups and race at the county level.
  • Data from 2000 to 2009 are based on intercensal population estimates and 2010-most current year are based on the postcensal population estimates.

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What time period of data is available?

  • The Iowa Public Health Tracking portal displays hospitalization data from the year 2000 through the most recent year of data available.
  • The bridged-race estimates are released by NCHS each year in July for the prior year (i.e. the 2016 population estimates are released in July 2017.)

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How are population estimates generated?

  • Bridged-race population estimates result from bridging the 31 race categories used in Census 2000 and Census 2010, 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 categories specified in the 1977 OMB standards.
  • The bridged-race population estimates are produced under a collaborative arrangement with the U. S. Census Bureau.
  • Race bridging refers to making data collected using one set of race categories consistent with data collected using a different set of race categories, to permit estimation and comparison of race-specific statistics at a point in time or over time.
  • More specifically, race bridging is a method used to make multiple-race and single-race data collection systems sufficiently comparable to permit estimation and analysis of race-specific statistics.

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What are the limitations of the data?

  • Certain populations such as the homeless or different age groups may be over- or undercounted.
  • Census survey questions may also be misunderstood.
  • Race and ethnicity are somewhat ambiguous characteristics that may not be as well defined as the data indicate.
  • Population estimates are real and temporal estimates of the population based on individuals. Individual risk factors are not accounted for in these data.

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Where can I find more technical information about the data?

More detailed documentation of the population data can be found in the following documents:

Indicator Profiles

Population Estimates pdf

Contact Us to learn more about population characteristics, population data, or any of the measures displayed on the Iowa Public Health Tracking Portal.

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