Lake County, IL population age distribution
A complete breakdown of Lake County's age demographics from 0 to 85 years, distributed across 18 age groups is listed in the table below.
Age Group | Population | % of Total Population |
---|---|---|
Under 5 years | 39,917 | 5.59% |
5 to 9 years | 47,777 | 6.69% |
10 to 14 years | 51,230 | 7.17% |
15 to 19 years | 55,947 | 7.83% |
20 to 24 years | 50,154 | 7.02% |
25 to 29 years | 40,052 | 5.61% |
30 to 34 years | 39,150 | 5.48% |
35 to 39 years | 45,996 | 6.44% |
40 to 44 years | 44,369 | 6.21% |
45 to 49 years | 48,293 | 6.76% |
50 to 54 years | 50,669 | 7.09% |
55 to 59 years | 51,936 | 7.27% |
60 to 64 years | 46,104 | 6.45% |
65 to 69 years | 35,181 | 4.92% |
70 to 74 years | 27,523 | 3.85% |
75 to 79 years | 16,769 | 2.35% |
80 to 84 years | 10,676 | 1.49% |
85 years and over | 12,741 | 1.78% |
TABLE OF CONTENTS
Lake County, IL population by age group
Sources: U.S. Census Bureau, American Community Survey (ACS) 2021

The largest age group in Lake County, IL was for the group of age 15-19 years with a population of 55,947 (7.83%), according to the 2021 American Community Survey.
At the same time, the smallest age group in Lake County, IL was the 80-84 years with a population of 10,676 (1.49%).
Lake County, IL population by age cohort
To better understand the age distribution of Lake County, IL's population, we divided it into the following 3 cohorts:
- Children : Under the age of 18 years
- Adults (working population): Between the age of 18 and 64 years
- Seniors: 65 years and above

Here's the population for each of the three cohorts.
Age Group | Population | % of Total Population |
---|---|---|
Under 18 years | 172,427 | 24.13% |
18 to 64 years | 439,167 | 61.47% |
85 years and over | 102,890 | 14.4% |
Key stats for each age cohort as per our analysis of U.S. Census Bureau American Community Survey:
- Lake County's population under 18 was 24.13%, compared to the 22.51% nationwide.
- Lake County's working population (between 18 and 64) was 61.47%, compared to 61.45% nationwide.
- Lake County's elderly or the senior population (over 65 age) was 14.40% as compared to 16.04% nationwide.
Lake County, IL population pyramid
Population pyramid for Lake County, IL is charted below using the estimates from U.S. Census Bureau's American Community Survey 5-Year estimates. A wide base suggests population increase, narrow base indicates declining birth rates.
Key stats from our analysis of the Lake County's population pyramid:
- Youth dependency ratio, which is the number of children aged 0-14 per 100 persons aged 15-64, for Lake County, IL, is 29.4.
- Old-age dependency ratio, which is the number of persons aged 65 or over per 100 persons aged 15-64, for Lake County, IL, is 21.8.
- Total dependency ratio for Lake County, IL is 51.2.
- Potential support ratio, which is the number of youth (working age population) per elderly, for Lake County, IL is 4.6.

Here's the Lake County, IL's male and female population across different age groups:
Age Group | Population(Male) | Population(Female) | Total Population |
---|---|---|---|
Under 5 years | 20,298 | 19,619 | 39,917 |
5 to 9 years | 24,712 | 23,065 | 47,777 |
10 to 14 years | 25,810 | 25,420 | 51,230 |
15 to 19 years | 29,733 | 26,214 | 55,947 |
20 to 24 years | 27,222 | 22,932 | 50,154 |
25 to 29 years | 21,046 | 19,006 | 40,052 |
30 to 34 years | 19,818 | 19,332 | 39,150 |
35 to 39 years | 23,503 | 22,493 | 45,996 |
40 to 44 years | 21,778 | 22,591 | 44,369 |
45 to 49 years | 24,050 | 24,243 | 48,293 |
50 to 54 years | 25,212 | 25,457 | 50,669 |
55 to 59 years | 26,507 | 25,429 | 51,936 |
60 to 64 years | 22,117 | 23,987 | 46,104 |
65 to 69 years | 17,265 | 17,916 | 35,181 |
70 to 74 years | 12,965 | 14,558 | 27,523 |
75 to 79 years | 7,503 | 9,266 | 16,769 |
80 to 84 years | 4,671 | 6,005 | 10,676 |
85 years and over | 4,701 | 8,040 | 12,741 |
Things to know
What is the population of Lake County, IL under 18?
Lake County's population under the age of 18 is 172,427, as per the latest U.S. Census Bureau's American Community Survey estimates. This population is 24.13% of the total resident population of Lake County, IL.
What is the aging population in Lake County, IL?
Lake County's population aged 65 years and above was 102,890. As per the U.S. Census Bureau's American Community Survey, this population is 14.40% of the entire population.
References
- U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates