The mySidewalk data library includes data from the U.S. Census Bureau American Community Survey (ACS). The ACS is an ongoing survey conducted by the U.S. Census Bureau to annually publish its hallmark data products, the ACS 5-Year Estimates and ACS 1-Year Estimates. The ACS survey replaced the long-form questionnaire beginning with the Decennial Census in 2010. 

Unlike the Decennial Census, which are counts of the entire population, the ACS collects data from a representative sample of the population. The sample collected over a single year powers the 1-Year Estimates. The Census Bureau produces the ACS 5-Year Estimates by pooling together the results of the five previous survey years. Through pooling multiple years of data, the 5-year estimates are a more accurate estimation than the 1-year estimates.

mySidewalk curates the current 5-Year ACS Estimates due to the improved value they provide to you as a data user: improved accuracy and granularity.

5-Year Estimates are significantly more accurate than 1-Year Estimates and have smaller margins of error. This improved accuracy comes from the larger sample size that comes with pooling multiple years of survey responses. This improved accuracy translates to greater statistical reliability, greater geographic coverage, and the ability to provide variables that would otherwise be suppressed by the Census due to insufficient statistical reliability. It also means the values are more stable year-to-year.

What does this mean for you?
​You can place more trust in 5-Year Estimates to accurately reflect conditions and trends in your community.
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5-Year Estimates are available for small geographies, going as small as block groups for the whole nation. 1-Year Estimates, by contrast, are only available for geographic areas with populations of 65,000 or more. Providing the 5-Year Estimates means that all communities, including small or rural communities, can quickly find and use data about their community. The 5-Year Estimates also benefit larger communities by showing differences across geographies within a single community, which helps departments better target services and policies to the neighborhoods with the greatest need, and to recognize where changes are occurring over time.

What does this mean for you?
You can always find and visualize data at the geographies that matter to you and your community.  Moreover, you can compare smaller geographies to benchmarks such as the state to better understand how your community is faring in key metrics.
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Many people believe 1-Year Estimates are “newer” or “more recent” than 5-Year Estimates.  First, the 5-Year estimates are just as current as 1-Year Estimates—the sampling for the 5-Year estimates includes the sample used for 1-Year estimates. That most recent sample is reflected in the pooled data value shown.  However, this common myth does get at some of the nuances of using 5-Year Estimates. 

A key consideration of using multi-year estimates is that, because the data is collected over a period of time, they don’t necessarily describe any specific day, month, or year within that time period. Additionally, significant, dramatic changes in the community that may occur over a single year may be “smoothed out” somewhat in the pooled sample. However, those changes are still collected and reflected in the overall value. 

What does this mean for you?
​The 5-Year Estimates are equally recent as 1-Year Estimates. If your community has experienced exceptional, dramatic change over the last 12 months, that change may be somewhat less pronounced in the 5-Year Estimates. However, they still provide a more reliable estimate for the overwhelming majority of communities.

Ready to learn more? You can find more information about ACS Estimates in the resources below:

mySidewalk’s most recent ACS Update

A detailed guide to using multi-year estimates from the U.S. Census

A “quick glance” guide to ACS estimates from the U.S. Census