Polk County, IA population age distribution
A complete breakdown of Polk 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 | 33,634 | 6.88% |
5 to 9 years | 32,822 | 6.71% |
10 to 14 years | 35,495 | 7.26% |
15 to 19 years | 31,558 | 6.46% |
20 to 24 years | 30,565 | 6.25% |
25 to 29 years | 37,580 | 7.69% |
30 to 34 years | 36,992 | 7.57% |
35 to 39 years | 35,831 | 7.33% |
40 to 44 years | 32,623 | 6.67% |
45 to 49 years | 30,353 | 6.21% |
50 to 54 years | 29,877 | 6.11% |
55 to 59 years | 31,561 | 6.46% |
60 to 64 years | 26,244 | 5.37% |
65 to 69 years | 22,197 | 4.54% |
70 to 74 years | 17,122 | 3.5% |
75 to 79 years | 10,086 | 2.06% |
80 to 84 years | 6,893 | 1.41% |
85 years and over | 7,438 | 1.52% |
TABLE OF CONTENTS
Polk County, IA population by age group
Sources: U.S. Census Bureau, American Community Survey (ACS) 2021

The largest age group in Polk County, IA was for the group of age 25-29 years with a population of 37,580 (7.69%), according to the 2021 American Community Survey.
At the same time, the smallest age group in Polk County, IA was the 80-84 years with a population of 6,893 (1.41%).
Polk County, IA population by age cohort
To better understand the age distribution of Polk County, IA'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 | 121,827 | 24.92% |
18 to 64 years | 303,308 | 62.04% |
85 years and over | 63,736 | 13.04% |
Key stats for each age cohort as per our analysis of U.S. Census Bureau American Community Survey:
- Polk County's population under 18 was 24.92%, compared to the 22.51% nationwide.
- Polk County's working population (between 18 and 64) was 62.04%, compared to 61.45% nationwide.
- Polk County's elderly or the senior population (over 65 age) was 13.04% as compared to 16.04% nationwide.
Polk County, IA population pyramid
Population pyramid for Polk County, IA 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 Polk County's population pyramid:
- Youth dependency ratio, which is the number of children aged 0-14 per 100 persons aged 15-64, for Polk County, IA, is 31.5.
- Old-age dependency ratio, which is the number of persons aged 65 or over per 100 persons aged 15-64, for Polk County, IA, is 19.7.
- Total dependency ratio for Polk County, IA is 51.3.
- Potential support ratio, which is the number of youth (working age population) per elderly, for Polk County, IA is 5.1.

Here's the Polk County, IA's male and female population across different age groups:
Age Group | Population(Male) | Population(Female) | Total Population |
---|---|---|---|
Under 5 years | 17,128 | 16,506 | 33,634 |
5 to 9 years | 15,954 | 16,868 | 32,822 |
10 to 14 years | 18,914 | 16,581 | 35,495 |
15 to 19 years | 15,906 | 15,652 | 31,558 |
20 to 24 years | 15,081 | 15,484 | 30,565 |
25 to 29 years | 18,817 | 18,763 | 37,580 |
30 to 34 years | 18,772 | 18,220 | 36,992 |
35 to 39 years | 17,956 | 17,875 | 35,831 |
40 to 44 years | 16,876 | 15,747 | 32,623 |
45 to 49 years | 15,415 | 14,938 | 30,353 |
50 to 54 years | 15,106 | 14,771 | 29,877 |
55 to 59 years | 15,647 | 15,914 | 31,561 |
60 to 64 years | 12,655 | 13,589 | 26,244 |
65 to 69 years | 10,451 | 11,746 | 22,197 |
70 to 74 years | 7,924 | 9,198 | 17,122 |
75 to 79 years | 4,194 | 5,892 | 10,086 |
80 to 84 years | 2,642 | 4,251 | 6,893 |
85 years and over | 2,860 | 4,578 | 7,438 |
Things to know
What is the population of Polk County, IA under 18?
Polk County's population under the age of 18 is 121,827, as per the latest U.S. Census Bureau's American Community Survey estimates. This population is 24.92% of the total resident population of Polk County, IA.
What is the aging population in Polk County, IA?
Polk County's population aged 65 years and above was 63,736. As per the U.S. Census Bureau's American Community Survey, this population is 13.04% of the entire population.
References
- U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates