Variables, and the values they represent, may change over time. Use this 2021 1YR API Changes document as a guide for which variables have changed from the prior year for 2021 ACS 1-Year Detailed Tables, Data Profiles and Subject Tables. See below for a description of each change type.
For table changes, check the ACS product changes webpage for source table changes.
In September 2016, ACS released annotation variables that return character representations of each estimate. Many annotations return as null. However, if an annotation variable returns a value, it provides important information about the estimate or margin of error. For example, if an estimate variable (variable ending in “E”) returns “-888888888”, the annotation variable will return “(X)”. Looking at the Notes on ACS Estimate and Annotation Values, this means the estimate is not applicable or not available. For a complete list of return values and their annotations, see: