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U.S. Census Bureau American Community Survey (ACS) 1-Year vs. 5-Year Estimates

Learn the difference between the U.S. Census Bureau's American Community Survey (ACS) 1-Year and 5-Year Estimates.

What is the ACS?

The American Community Survey (ACS) is an ongoing survey conducted by the U.S. Census Bureau. It collects detailed demographic, social, economic, and housing data annually. Unlike the Decennial Census, which counts the entire population, the ACS surveys a representative sample to estimate broader trends.

The ACS publishes two main types of estimates:

  • 1-Year Estimates: Based on data collected in a single year.
  • 5-Year Estimates: Pooled data from five consecutive years.

Detailed comparison: 1-Year vs. 5-Year Estimates

Feature 1-year Estimates 5-year Estimates
Sample Size Data from one year Data pooled from five years
Geographic Coverage Large areas (65,000+ population) Small areas (block groups and larger)
Trend Stability Captures recent changes, more variability Smoothed trends over time

Common myths about recency

Some believe 1-Year Estimates are more recent than 5-Year Estimates. However, 5-Year Estimates include the most current year’s data within their pooled values. If a dramatic change occurred in the past year, it might be less pronounced in the 5-Year Estimates but is still reflected.

When to use each

  • 1-Year Estimates: If your community experienced rapid, significant changes in the past year.
  • 5-Year Estimates: For most use cases, especially when prioritizing accuracy or analyzing smaller geographies.

Tip: Best practice is consistency. Whichever ACS estimates you pick, you should consistently use only 5-year or only 1-year estimates for all of the data visualizations on a given presentation, report, dashboard, or website.

Coming in 2025

We are excited to announce two enhancements planned for 2025:

  1. 1-Year Estimates - ✅ Added September 2025
    1. For use in geographies with 65,000 people or more when the year-to-year trend is more important than granularity and stability.
  2. Non-Overlapping 5-Year Estimates
    1. We will add non-overlapping ACS 5-Year Estimates and restructure the time groupings so that you can view trends over time with only ACS data.

These updates will provide greater flexibility and deeper insights for all users.