Where does the income data come from?
The most current income statistics from the US Census Bureau for zip codes/ZCTAS are the American Community Survey’s 2021 5-year estimates, which also include data such as income, poverty, language, and other important demographics. The 2021 ACS uses data collected from 2017 to 2021 to produce demographic estimates for zip codes/ZCTAS for 2021. They adjust the income reported in 2017 to 2021 dollars to account for inflation.
What is the American Community Survey?
Most folks are familiar with the US Census Bureau's Decennial Census that sends a survey out to all (ideally!) US households. But what's not as well known is that the US Census Bureau also collects data each year from a much smaller sample of US households. They use this annual data to produce a dataset called the American Community Survey.
The American Community Survey (or the ACS) is the ongoing, annual survey of the social, economic, housing, and demographic characteristics of the nation’s population. It is sent out monthly to ~3.5 million addresses and informs over $675 billion of Federal government spending each year.
The ACS covers topics such as educational attainment, internet access, transportation, employment, among others and is good for obtaining population characteristics (percents, means, medians, and rates) rather than population counts.
This dataset is released in 3 parts each year:
- 1-year Estimates for geographies with a total population of 65,000 or more
- 1-year Supplemental Estimates for geographies with a total population of 20,000 - 64,999
- 5-year Estimates for geographies with a total population of less than 20,00
- The 5-year estimates combine data from the most recent five years to create a more reliable estimate for small geographies (down to the block group level).
- The 2021 ACS data currently available combines data collected from 2017, 2018, 2019, 2020 and 2021 for example.
A Short History of the American Community Survey
- 1790 - The first census was conducted and occurred every 10 years using one form to collect data.
- 1940 - The decennial census began using a short form for all households and a long form for a sample of households.
- 1990's - The long form data was recognized as becoming less and less current as the decade went on.
- 2005 - The ACS was implemented to collect data for all of America's communities each year.
ACS Data vs. Census Data
For even more exciting details about Census data, you can read the "Income in the Past 12 Months" section in the Census’ Subject Definitions document.
US Census Bureau
Tippett, R. (2021, November 15). What you need to know about the 2020 American Community Survey. Retrieved November 19, 2021, from https://www.ncdemography.org/2021/11/15/what-you-need-to-know-about-the-2020-american-community-survey/