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San Mateo County, CA Population by Age

The median age in San Mateo County, CA is 40.0, as per 2021 ACS 5-Year Estimates. Of the total population, 16.92% were under the age of 15, 17.67% aged 15 to 29, 49.16% aged 30 to 64, 13.90% aged 65 to 84, and 2.34% were 85 years of age and older.
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By Neilsberg Research
Updated Sep 17, 2023

San Mateo County, CA population age distribution

A complete breakdown of San Mateo 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 41,711 5.47%
5 to 9 years 43,385 5.69%
10 to 14 years 43,955 5.76%
15 to 19 years 41,310 5.42%
20 to 24 years 40,420 5.3%
25 to 29 years 53,025 6.95%
30 to 34 years 59,085 7.75%
35 to 39 years 58,921 7.73%
40 to 44 years 51,768 6.79%
45 to 49 years 53,146 6.97%
50 to 54 years 52,027 6.82%
55 to 59 years 52,626 6.9%
60 to 64 years 47,240 6.2%
65 to 69 years 40,484 5.31%
70 to 74 years 30,628 4.02%
75 to 79 years 20,536 2.69%
80 to 84 years 14,343 1.88%
85 years and over 17,878 2.34%
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TABLE OF CONTENTS

San Mateo County, CA population by age group

Key stats
210,781
Population under 25 years
222,799
Population aged 25-44
205,039
Population aged 45-64
123,869
Population aged 65+

Sources: U.S. Census Bureau, American Community Survey (ACS) 2021

The graph shows San Mateo County's population by age group, with age group on x-axis and the respective age group's percent of the total population on y-axis
San Mateo County, CA population by age group. The largest age group was 30-34 years with a poulation of 59,085 (7.75% of the total population). Source: U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

The largest age group in San Mateo County, CA was for the group of age 30-34 years with a population of 59,085 (7.75%), according to the 2021 American Community Survey.

At the same time, the smallest age group in San Mateo County, CA was the 80-84 years with a population of 14,343 (1.88%).

San Mateo County, CA population by age cohort

To better understand the age distribution of San Mateo County, CA'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
The pie chart shows San Mateo County's population divided into segments, with each segment representing an age cohort. The area of each segment is in the same proportion of a circle as the population of the cohort is of the total population.
San Mateo County, CA population by age cohorts (Children: Under 18 years; Working population: 18-64 years; Senior population: 65 years or more). The largest age group was 18 - 64 years with a poulation of 482,834 (63.32% of the total population). Source: U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

Here's the population for each of the three cohorts.

Age Group Population % of Total Population
Under 18 years 155,785 20.43%
18 to 64 years 482,834 63.32%
85 years and over 123,869 16.25%
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Key stats for each age cohort as per our analysis of U.S. Census Bureau American Community Survey:

  • San Mateo County's population under 18 was 20.43%, compared to the 22.51% nationwide.
  • San Mateo County's working population (between 18 and 64) was 63.32%, compared to 61.45% nationwide.
  • San Mateo County's elderly or the senior population (over 65 age) was 16.25% as compared to 16.04% nationwide.

San Mateo County, CA population pyramid

Population pyramid for San Mateo County, CA 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 San Mateo County's population pyramid:

  • Youth dependency ratio, which is the number of children aged 0-14 per 100 persons aged 15-64, for San Mateo County, CA, is 25.3.
  • Old-age dependency ratio, which is the number of persons aged 65 or over per 100 persons aged 15-64, for San Mateo County, CA, is 24.3.
  • Total dependency ratio for San Mateo County, CA is 49.6.
  • Potential support ratio, which is the number of youth (working age population) per elderly, for San Mateo County, CA is 4.1.
The graph shows San Mateo County's population across different age group and gender, with population on x-axis and population y-axis. The male population is plotted on the left in blue color whereas the female population is plotted on the right in pink color.
San Mateo County, CA population pyramid i.e. San Mateo County population distrubution across age and gender. Source: U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

Here's the San Mateo County, CA's male and female population across different age groups:

Age Group Population(Male) Population(Female) Total Population
Under 5 years 21,474 20,237 41,711
5 to 9 years 22,568 20,817 43,385
10 to 14 years 22,218 21,737 43,955
15 to 19 years 21,387 19,923 41,310
20 to 24 years 20,850 19,570 40,420
25 to 29 years 27,726 25,299 53,025
30 to 34 years 30,710 28,375 59,085
35 to 39 years 30,266 28,655 58,921
40 to 44 years 25,798 25,970 51,768
45 to 49 years 26,706 26,440 53,146
50 to 54 years 26,044 25,983 52,027
55 to 59 years 25,623 27,003 52,626
60 to 64 years 23,405 23,835 47,240
65 to 69 years 19,867 20,617 40,484
70 to 74 years 13,317 17,311 30,628
75 to 79 years 8,840 11,696 20,536
80 to 84 years 5,943 8,400 14,343
85 years and over 6,884 10,994 17,878
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Things to know

What is the population of San Mateo County, CA under 18?

San Mateo County's population under the age of 18 is 155,785, as per the latest U.S. Census Bureau's American Community Survey estimates. This population is 20.43% of the total resident population of San Mateo County, CA.

What is the aging population in San Mateo County, CA?

San Mateo County's population aged 65 years and above was 123,869. As per the U.S. Census Bureau's American Community Survey, this population is 16.25% of the entire population.

References

Datasets

San Mateo County, CA Age Group Population Dataset: A complete breakdown of San Mateo County age demographics from 0 to 85 years, distributed across 18 age groups
ACS
Free
Neilsberg
CSV, JSON
2017-2021
CC BY 4.0
About this dataset

Context

The dataset tabulates the San Mateo County population distribution across 18 age groups. It lists the population in each age group along with the percentage population relative of the total population for San Mateo County. The dataset can be utilized to understand the population distribution of San Mateo County by age. For example, using this dataset, we can identify the largest age group in San Mateo County.

Key observations

The largest age group in San Mateo County, CA was for the group of age 30-34 years with a population of 59,085 (7.75%), according to the 2021 American Community Survey. At the same time, the smallest age group in San Mateo County, CA was the 80-84 years with a population of 14,343 (1.88%). Source: U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

San Mateo County population by age group

Content

When available, the data consists of estimates from the U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

Age groups:

  • Under 5 years
  • 5 to 9 years
  • 10 to 14 years
  • 15 to 19 years
  • 20 to 24 years
  • 25 to 29 years
  • 30 to 34 years
  • 35 to 39 years
  • 40 to 44 years
  • 45 to 49 years
  • 50 to 54 years
  • 55 to 59 years
  • 60 to 64 years
  • 65 to 69 years
  • 70 to 74 years
  • 75 to 79 years
  • 80 to 84 years
  • 85 years and over

Variables / Data Columns

  • Age Group: This column displays the age group in consideration
  • Population: The population for the specific age group in the San Mateo County is shown in this column.
  • % of Total Population: This column displays the population of each age group as a proportion of San Mateo County total population. Please note that the sum of all percentages may not equal one due to rounding of values.

Good to know

Margin of Error

Data in the dataset are based on the estimates and are subject to sampling variability and thus a margin of error. Neilsberg Research recommends using caution when presening these estimates in your research.

Custom data

If you do need custom data for any of your research project, report or presentation, you can contact our research staff at research@neilsberg.com for a feasibility of a custom tabulation on a fee-for-service basis.

Inspiration

Neilsberg Research Team curates, analyze and publishes demographics and economic data from a variety of public and proprietary sources, each of which often includes multiple surveys and programs. The large majority of Neilsberg Research aggregated datasets and insights is made available for free download at https://www.neilsberg.com/research/.

Recommended for further research

This dataset is a part of the main dataset for San Mateo County Population by Age. You can refer the same here

San Mateo County, CA Age Cohorts Dataset: Children, Working Adults, and Seniors in San Mateo County - Population and Percentage Analysis
ACS
Free
Neilsberg
CSV, JSON
2017-2021
CC BY 4.0
About this dataset

Context

The dataset tabulates the San Mateo County population by age cohorts (Children: Under 18 years; Working population: 18-64 years; Senior population: 65 years or more). It lists the population in each age cohort group along with its percentage relative to the total population of San Mateo County. The dataset can be utilized to understand the population distribution across children, working population and senior population for dependency ratio, housing requirements, ageing, migration patterns etc.

Key observations

The largest age group was $b3_v1 with a poulation of $b3_v2 ($b3_v3 of the total population). Source: U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

San Mateo County population by age cohort

Content

When available, the data consists of estimates from the U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

Age cohorts:

  • Under 18 years
  • 18 to 64 years
  • 65 years and over

Variables / Data Columns

  • Age Group: This column displays the age cohort for the San Mateo County population analysis. Total expected values are 3 groups ( Children, Working Population and Senior Population).
  • Population: The population for the age cohort in San Mateo County is shown in the following column.
  • Percent of Total Population: The population as a percent of total population of the San Mateo County is shown in the following column.

Good to know

Margin of Error

Data in the dataset are based on the estimates and are subject to sampling variability and thus a margin of error. Neilsberg Research recommends using caution when presening these estimates in your research.

Custom data

If you do need custom data for any of your research project, report or presentation, you can contact our research staff at research@neilsberg.com for a feasibility of a custom tabulation on a fee-for-service basis.

Inspiration

Neilsberg Research Team curates, analyze and publishes demographics and economic data from a variety of public and proprietary sources, each of which often includes multiple surveys and programs. The large majority of Neilsberg Research aggregated datasets and insights is made available for free download at https://www.neilsberg.com/research/.

Recommended for further research

This dataset is a part of the main dataset for San Mateo County Population by Age. You can refer the same here

San Mateo County, CA Population Pyramid Dataset: Age Groups, Male and Female Population, and Total Population for Demographics Analysis
ACS
Free
Neilsberg
CSV, JSON
2017-2021
CC BY 4.0
About this dataset

Context

The dataset tabulates the data for the San Mateo County, CA population pyramid, which represents the San Mateo County population distribution across age and gender, using estimates from the U.S. Census Bureau American Community Survey 5-Year estimates. It lists the male and female population for each age group, along with the total population for those age groups. Higher numbers at the bottom of the table suggest population growth, whereas higher numbers at the top indicate declining birth rates. Furthermore, the dataset can be utilized to understand the youth dependency ratio, old-age dependency ratio, total dependency ratio, and potential support ratio.

Key observations

  • Youth dependency ratio, which is the number of children aged 0-14 per 100 persons aged 15-64, for San Mateo County, CA, is 25.3.
  • Old-age dependency ratio, which is the number of persons aged 65 or over per 100 persons aged 15-64, for San Mateo County, CA, is 24.3.
  • Total dependency ratio for San Mateo County, CA is 49.6.
  • Potential support ratio, which is the number of youth (working age population) per elderly, for San Mateo County, CA is 4.1.

San Mateo County population pyramid

Content

When available, the data consists of estimates from the U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates.

Age groups:

  • Under 5 years
  • 5 to 9 years
  • 10 to 14 years
  • 15 to 19 years
  • 20 to 24 years
  • 25 to 29 years
  • 30 to 34 years
  • 35 to 39 years
  • 40 to 44 years
  • 45 to 49 years
  • 50 to 54 years
  • 55 to 59 years
  • 60 to 64 years
  • 65 to 69 years
  • 70 to 74 years
  • 75 to 79 years
  • 80 to 84 years
  • 85 years and over

Variables / Data Columns

  • Age Group: This column displays the age group for the San Mateo County population analysis. Total expected values are 18 and are define above in the age groups section.
  • Population (Male): The male population in the San Mateo County for the selected age group is shown in the following column.
  • Population (Female): The female population in the San Mateo County for the selected age group is shown in the following column.
  • Total Population: The total population of the San Mateo County for the selected age group is shown in the following column.

Good to know

Margin of Error

Data in the dataset are based on the estimates and are subject to sampling variability and thus a margin of error. Neilsberg Research recommends using caution when presening these estimates in your research.

Custom data

If you do need custom data for any of your research project, report or presentation, you can contact our research staff at research@neilsberg.com for a feasibility of a custom tabulation on a fee-for-service basis.

Inspiration

Neilsberg Research Team curates, analyze and publishes demographics and economic data from a variety of public and proprietary sources, each of which often includes multiple surveys and programs. The large majority of Neilsberg Research aggregated datasets and insights is made available for free download at https://www.neilsberg.com/research/.

Recommended for further research

This dataset is a part of the main dataset for San Mateo County Population by Age. You can refer the same here

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San Mateo County, CA Demographics San Mateo County, CA Population

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Neilsberg Research
Neilsberg Research team are data scientists with expertise in processing, analysis and visualization of big data helping small businesses make right decisions.
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Collection 5 Resources