Confirm if CPS data includes health insurance premiums withheld from Social Security

The MO Form-5695 Worksheet for deducting qualified health insurance premiums starts off with a section especially for individuals who have health insurance premiums withheld from their Social Security checks - we do not currently model this, and it is unclear how often this comes up.

Need to investigate whether withheld premiums are a part of CPS data, whether individually or rolled up into some other variable(s). If not already included, we will need to add variable.

Form is here: https://dor.mo.gov/forms/5695.pdf

Start by reviewing the MO Form-5695 worksheet and the CPS data definitions to determine whether premiums withheld from Social Security are represented individually or through another variable. The issue names no repository files or tests; done means documenting whether the data already includes this amount or identifying the variable addition required.

Written by the indexing model from the issue text.