The State Reports for County-Level Data on Prevalence are designed to provide the users of disability statistics with the number of people with disabilities for any given state and county in the United States. This report is intended to be an online complement to Section 1: Population and Prevalence of the Annual Disability Statistics Compendium and Annual Disability Statistics Supplement, providing greater detail within each state. The State Reports for County-Level Data on Prevalence can be used to compare county-level statistics between counties in any given state or states.

The following report provides county-level statistics for Illinois. The proportions of people with disabilities, sometimes called prevalence, presented in the State Reports for County-Level Data is a useful tool for advocates, researchers, and policy-makers to plan and provide services and supports for people with disabilities. In this report, the prevalence of people with disabilities is presented as the number of people with disabilities in a given state and county per total state and county populations, respectively. Counts and percentages are provided in tables and maps.

The data for this report come from the American Community Survey 5-year data. The American Community Survey (ACS) is a national survey developed by the U.S. Census Bureau to provide information on a number of topics about social, economic, and demographic characteristics of the U.S. population. ACS 5-year data is collected over a longer period of time than 1-year data, providing larger sample sizes and increased reliability for less populated areas and small population subgroups. All of the statistics in this report use the ACS 5-year data which includes data from the year of the report and data from the four previous years. In the ACS, people are identified as having a disability based on responses to a series of six questions asking about having difficulties with vision, hearing, ambulation, cognition, self-care, and independent living (see glossary for further details).

Specific to Illinois, the state chosen for this report, sentences providing interpretation and context for prevalence statistics are included below. A short glossary of terms is also provided at the end of the report explaining the statistics that are illustrated in each sentence.

Additional Resources. The Annual Disability Statistics Compendium and its complement, the Annual Disability Statistics Supplement, are summaries of statistics about people with disabilities, available both in hard copy and online at https://www.disabilitycompendium.org.

Help navigating any of the resources described here can be found in the Frequently Asked Questions section at https://www.disabilitycompendium.org/faq. Assistance interpreting and locating additional statistics is available via our toll-free number, 866.538.9521, or by email, disability.statistics@unh.edu. For more information about our research projects, please visit https://www.researchondisability.org.

Suggested Citation. Boege, S.L., Lauer, E.A., & Houtenville, A.J., 2020. 2018 State Report for Illinois County-Level Data: Prevalence. Durham, NH: University of New Hampshire, Institute on Disability.

The following statements are designed to help understand the 2018 county-level statistics from Illinois that are presented:

• For the number of people with and without disabilities:
  • The range of total people across Illinois counties, also known as the difference between the largest and smallest counts of people across Illinois counties, was 5,173,322.
    • The county with the greatest number of total people was Cook (5,177,243 people).
    • The county with the least number of total people was Hardin (3,921 people).
  • The average number of total people across all counties was 123,953.
  • The median, also known as the middle-most number, of total people across Illinois counties was 24,778.

• For the number of people with disabilities:
  • The range of people with disabilities across Illinois counties, also known as the difference between the largest and smallest counts of people with disabilities across Illinois counties, was 525,748.
    • The county with the greatest number of people with disabilities was Cook (526,347 people).
    • The county with the least number of people with disabilities was Scott (599 people).
  • The average number of people with disabilities across all counties was 13,551.
  • The median, also known as the middle-most number, of people with disabilities across Illinois counties was 3,602.

• For the percentage of people with disabilities:
  • For the entire state of Illinois, the overall percentage of people with disabilities is 10.9%.
    • The county with the highest percentage of people with disabilities was Hardin (25.7%).
    • The county with the lowest percentage of people with disabilities was Kendall (7.7%).

• For the number of people without disabilities:
  • The range of people without disabilities across Illinois counties, also known as the difference between the largest and smallest counts of people without disabilities across Illinois counties, was 4,647,984.
    • The county with the greatest number of people without disabilities was Cook (4,650,896 people).
    • The county with the least number of people without disabilities was Hardin (2,912 people).
  • The average number of people without disabilities across all counties was 110,402.
  • The median, also known as the middle-most number, of people without disabilities across Illinois counties was 20,410.
• For the percentage of people without disabilities:
  • For the entire state of Illinois, the overall percentage of people without disabilities is 89.1%.
    • The county with the highest percentage of people without disabilities was Kendall (92.3%).
    • The county with the lowest percentage of people without disabilities was Hardin (74.3%).

There are a number of concepts and factors which complicate the interpretation of the estimates presented in this report. These concerns affect all statistics from population-based surveys. The estimates included in this document should be interpreted the following limitations in mind and generalized with caution. In each point, a link to the U.S. Census Bureau website describing the limitation or concept in greater detail in the ACS has been provided.

• Statistics are based on a sample and subject to sample variation

• Statistics based on a sample may not fully represent the total U.S. population

• People responding to the ACS may be different than people not responding

• When people do not respond to all ACS questions their responses are created based on assignment or allocation

Additional links to resources for the ACS:

• Information on the disability questions

• ACS design and methodology

• ACS questionnaire and instructions

American Community Survey (ACS) — The American Community Survey is a large, continuous demographic survey conducted by the U.S. Census Bureau that will provide accurate and up-to-date profiles of America’s communities every year. Annual and multiyear estimates of population and housing data are generated for small areas, including tracts and population subgroups. This information is collected by mailing questionnaires to a sample of addresses. See the U.S. Census Bureau website for additional details.

The Six Disability Questions in the American Community Survey:

1. Is this person deaf or does he/she have serious difficulty hearing? (yes or no)
2. Is this person blind or does he/she have serious difficulty seeing even when wearing glasses? (yes or no)
3. (If person 5 years old or over) Because of a physical, mental, or emotional condition, does this person have serious difficulty concentrating, remembering, or making decisions? (yes or no)
4. (If person 5 years or old over) Does this person have serious difficulty walking or climbing stairs? (yes or no)
5. (If person 5 years old or over) Does this person have difficulty dressing or bathing? (yes or no)
6. (If person 15 years old or over) Because of a physical, mental, or emotional condition, does this person have difficulty doing errands alone such as visiting a doctor’s office or shopping? (yes or no)

Average — The sum of all of the values in a sample divided by the number of values in the sample.

Civilian — A person not in active-duty military.

Median — The middlemost value of a sample that separates the upper half of the values from the lower half of the values. 

Non-Institutionalized Population — Describes individuals who are residing in the community and who are not living in institutions such as jails, prisons, nursing homes, hospitals, etc.

Population — The total number of inhabitants in a defined geographic area including all races, classes, and groups.

Prevalence — The proportion of the population with a particular status or condition. Prevalence is usually expressed as a percentage or a number of people per unit of the population.

Prevalence Rate — The prevalence of a particular status or condition estimated over a specific period of time.

Range — The difference between the largest and smallest values in a sample. In a sample, when the smallest value is subtracted from the largest value the resulting value is called the range. 

Sampling Variability — The variation of a statistic when estimated from repeated samples.

United States Census Bureau — An agency within the United States Federal Statistical System tasked with producing data about the American people and economy. Their primary task is to conduct the United States Census every ten years.

About the Center

Rehabilitation Research and Training Center on Disability Statistics and Demographics (StatsRRTC)

Led by the University of New Hampshire, the StatsRRTC is a collaborative effort involving the following partners: American Association of People with Disabilities, Center for Essential Management Services, Council of State Administrators of Vocational Rehabilitation, Kessler Foundation, Mathematica Policy Research, and Public Health Institute.

The StatsRRTC is funded by the U.S. Department of Health and Human Services, Administration for Community Living, National Institute on Disability, Independent Living and Rehabilitation Research under grant number 90RTGE00010100, from 2018–2023.

Employment Policy and Measurement Rehabilitation Research and Training Center (EPM-RRTC)

Led by the University of New Hampshire, the EPM-RRTC is a collaborative effort involving the following partners: Association of University Centers on Disability, Hunter College, Kessler Foundation, Mathematica Policy Research, and the University of Chicago.

The EPM-RRTC is funded by the U.S. Department of Health and Human Services, Administration for Community Living, National Institute on Disability, Independent Living and Rehabilitation Research under grant number 90RT503701, from 2015–2020.

Contact Information
University of New Hampshire, Institute on Disability
10 West Edge Drive, Suite 101
Durham, NH 03824
Toll-Free Telephone/TTY: 866-538-9521
E-mail: Disability.Statistics@unh.edu
https://www.researchondisability.org