What are "data quality flags"?

What are “data quality flags”?

Many variables in the IPUMS have been edited for missing, illegible and inconsistent values. Data quality flags indicate which values are edited or allocated. More information on the philosophy and procedures used for editing and allocating the IPUMS data can be found on the Introduction to data editing and allocation page.

Each data quality flag corresponds to one or more IPUMS variables, and the codes for each flag vary based on the sample. Data quality flags can be included in your extract by selecting the boxes in the “Set Variable Options” step of the extract system.