Age
The American Community Survey (ACS) has been conducted on an ongoing basis for the entire country since 2005. Annually, calendar-year ACS results are released for areas with a population of at least 65,000. Due to the small sample size, single-year estimates are not available for less-populous areas. Combined estimates for three years of data are available annually for areas with a population of at least 20,000; five years of data are combined for less populous areas. The substantial sampling error present in the ACS is discussed in the data quality comments section below.
The ACS questionnaire asks respondents to supply the age of each person in two ways: in years and by providing the exact birth date. On Arizona Indicators, the age data are presented in five- or 10-year age groups. Annual data since 2005 are presented for the United States and Arizona, but data for each of the 15 Arizona counties are limited to a five-year average due to the substantial sampling error.
U. S. Department of Commerce, Census Bureau http://factfinder2.census.gov/faces/nav/jsf/pages/index.xhtml. Annual ACS estimates are released in September; five-year averages are available in December.
The Census Bureau publishes the ACS sampling error with every estimate, expressed as the margin of error with 90 percent confidence. The following is an example:
The estimate of the poverty rate in Maricopa County in 2009 was 15.2 percent, with a margin of error of + or – 0.6 percentage points. The interpretation is that there is a 90 percent likelihood that the actual poverty rate was within the confidence interval of 14.6 percent to 15.8 percent. A one-in-ten chance exists that the real rate was outside this range.
For the nation and other very populous areas, the annual ACS estimates are highly accurate. For moderately populous areas such as Arizona, sampling error is moderately large, so caution is urged in using the annual ACS data for the state. The sampling error for less populous areas, such as most of Arizona’s counties, is quite large, even when using five-year averages. Thus, considerable caution is urged in using the five-year ACS data for counties other than Maricopa and Pima.
The published margin of error should be taken into consideration when deciding whether to use a result from the ACS. Whether the reported sampling error is too large depends on the user’s purpose for accessing the data and on the volatility of the measure over time and across geographic areas.In addition to the sampling error, respondents do not always accurately report age or birth date.
Age Distribution in Arizona, 2013
Visualization Notes:
Using five-year age groups, the proportions of the Arizona population are highest in those groups between the ages of 5 and 24. The proportions fall sharply after age 54.
Age Distribution, Arizona Less United States
Visualization Notes:
Relative to the national average, the age distribution in Arizona is tilted toward children under the age of 15 and adults between 65 and 79 years of age. In contrast, Arizona has relatively few residents between the ages of 45 and 59.
Percentage of the Population in Age Groups
Visualization Notes:
Between 2005 and 2013, modest changes occurred in the age distribution of both the Arizona and national populations. The proportions of adults between the ages of 35 and 44 decreased and between the ages of 55 and 74 increased, as the baby-boom generation (those born from 1946 through 1964) aged. The percentage of children under the age of 15 declined. The percentages fluctuate annually in Arizona, likely due to sampling error.
Median Age, 2009-to-2013 Average
Visualization Notes:
On average between 2009 and 2013, the median age in Arizona (36.3) was a little less than the national average (37.3). In populous Maricopa County, the median age was only 35.0. The lowest median was in Coconino County at 31.0. In four counties — Gila, La Paz, Mohave, and Yavapai — the median age exceeded 47.
Percentage of the Population in Age Groups, 2009-to-2013 Average
Visualization Notes:
In Gila, La Paz, Mohave, and Yavapai counties, the proportion of the population 55 or older was far higher than the U.S. average between 2009 and 2013, with lower proportions of younger age cohorts. Apache and Santa Cruz counties had above-average shares of children and below-average shares of those between 20 and 54 years of age. Coconino County had a high percentage of those 20-to-54 years old and a below-average share 55 or older.
Percentage of the Population 55 Years and Older, 2009-to-2013 Average
Visualization Notes:
In Gila, La Paz, Mohave, and Yavapai counties, the proportion of the population 55 or older was far higher than the U.S. average between 2009 and 2013, with lower proportions of younger age cohorts. Apache and Santa Cruz counties had above-average shares of children and below-average shares of those between 20 and 54 years of age. Coconino County had a high percentage of those 20-to-54 years old and a below-average share 55 or older.
Data Source
U. S. Department of Commerce, Census Bureau http://factfinder2.census.gov/faces/nav/jsf/pages/index.xhtml. Annual ACS estimates are released in September; five-year averages are available in December.
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