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The American Community Survey (ACS) Office is currently testing a new format of the ACS Summary File (SF).


The current ACS SF is a comma-delimited text file that contains all Detailed Tables for the ACS.  The information is stored in a series of files, or sequences, and are divided by geographies, estimates, and margins of error. Users must merge together these different files to reproduce the complete tables. 

The Problem

The current format of the ACS SF is confusing for data users, and it is also extra work for ACS staff to support two different deliveries. For data users, multiple sources of technical documentation is needed to discover which file or sequence contains the table of interest, then must combine three files to recreate this table. For ACS staff, each year they must split the data into 140,000 files and prepare the same information into two different formats to accomate the requirements for the ACS SF and also the API, which then loads into ACS staff must also maintain thousands of lines of code for each vintage year and provide public trainings throughout the year.

In short, the issues with the ACS SF include a complex and confusing format, as well as excess work for both data users and the ACS staff.

Proposed Change

The American Community Survey Office plans to streamline the ACS SF production by delivering only one file. Instead of splitting the files by state and sequence number, the new format will be by table ID (see image below). That is, we would post a file for each table containing the estimates and margins of error for all available geographies.  This will reduce the complexity of the ACS SF from over 140,000 files to about 1,000 files, improve ease of use for data users, and lower the cost of creating, verifying and supporting the ACS SF compared to its current format. 

Benefits of the Change

For Data Users:

1. Estimates and margins of error for each table are combined into one file - This eliminates confusing sequences and logical record numbers.

2. All geography identifiers and labels combined into one file - Users will no longer need to search through multiple files for geography labels, they will all already be together.

3. Simplified documentation - Reducing the ACS SF complexity makes documentation much easier to understand.

For the American Community Survey Office:

Save time and resources - American Community Survey staff will be able to provide the ACS SF in an easier to use format.


The new Summary File contains three file types:

1. Table Labels - Labels for table estimates

  • ACS2018_Table_Shells.xlsx

  • Example: B01001_003 = “SEX BY AGE - Total Males Under 5 Years”

​2. Geography Labels - All geography labels within one file

  • 20181YRGeos.csv, 20185YRGeos.csv

  • Example: 04000US06 = “California”

3. Data Files - Data organized by table

  • 1YRData, 5YRData

  • Example: B01001_003E for 04000US06 = 1,243,103

Getting Started

Check out our proposed format and documentaion, downloadable from our FTP site.

Provide Feedback

To provide feedback on the proposed changes to the ACS SF format, please comment in this discussion form on the ACS Data Users Group site, or send an email to with the subject "ACS SF Feedback".

We would very much appreciate any complements or constructive criticism. Please be as specific as possible. 

We ask that you send all feedback in to us by Friday, November 13, 2020.

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