Detailed Tables for similar subject areas are grouped together in "sequences". A sequence number is an assigned number to a grouping of ACS tables.
Table sequencing now follows these new rules:
1) Tables are sorted numerically by the "root" of their Table ID, where the "root" is defined as the numeric section after the first letter and before any additional letters, so for example the root of B06004APR is "06004".
For tables with the same root, additionally sort them in the following order:
Non-iterated, non-collapsed, non-PR version (e.g., Table B06003)
Iterated, non-collapsed, non-PR versions (e.g., Tables B06004A, B06004B...B06004I)
Non-iterated, collapsed, non-PR version (e.g., Table C06001)
Iterated, collapsed, non-PR version (e.g., Tables C08505A, C08505B... C08505I)
Non-iterated, non-collapsed, PR version (e.g., Table B06003PR)
Iterated, non-collapsed, PR versions (e.g., Tables B06004APR, B06004BPR... B06004IPR)
Non-iterated, collapsed, PR version (e.g., Table C06001PR)
Iterated, collapsed, PR version (e.g., Table C06001APR)
2) With tables sorted in this order, start with the first table and assign it to the first sequence. For each subsequent table, if the table has either a new "subject," a new "geography type," or would cause the number of cells in the sequence to exceed 245, then start a new sequence. "Subject" is described using the second and third characters in the Table ID, so for example the subject of B06004APR is "06" for place of birth. You can view a complete list of subjects at ask.census.gov/faq.php?id=5000&faqId=1687
"Geography type" can be one of three things:
Place of Residence geography type,
Place of Work geography type, or
Residence 1 Year Ago geography type.
3) If a table does not fit in one sequence, then put the first 245 cells of it in one sequence, and the rest in the next. If a table does not fit in two sequences, then put the first 245 cells of it in one sequence, the next 245 cells of it in the next sequence, and the rest in a third sequence. The rules governing how many tables can be assigned the same sequence number depend on the following:
- There are no more than 256 cells per sequence, so the data can be read into a spreadsheet. There are 245 data cells and 11 other cells reserved for identifying information.
- There are approximately 170+ sequences for the 2013 ACS 1-year Summary File, approximately 170+ sequences for the 2011-2013 ACS 3-year Summary File, and approximately 120+ sequences for the 2009-2013 ACS 5-year Summary File.
- Tables are grouped numerically by the "root" of their Table ID, (i.e., Table B00001 is in sequence file 0001).
- Tables with race iterations are grouped in the same sequence.
It is critical to know the sequence number associated with a Detailed Table (Table ID) for two reasons. First, one needs it in order to access the correct estimates and margins of error files for the desired table. Second, the field start position for the estimates or margins of error of a certain Detailed Table depends on its sequence number. The Sequence Number and Detailed Table Number Lookup file, available as an Excel spreadsheet, text file, and SAS dataset, lists Table IDs associated with each sequence number. This spreadsheet is available on the ACS Summary File page at www.census.gov/acs/www/data_documentation/summary_file/
For example, to find the sequence number associated with the table B08406, a user must open and look for that Table ID in the Sequence Number and Table Number Lookup file. Shown below is a screenshot of this file opened to where the "tblid" is B08406. The next column in the file, "seq", shows that this Table ID is associated with the sequence number "0029". In order to access the estimate and margin of error file for Table B08406, a user will need to download the estimate and margin of error files labeled with the sequence number "0029".