What is NIU in ATUS data

I computed the variable of telework due to covid “COVIDTELEW”
using 2020 ATUS data and got the following results.

Yes 15%
No 29%
NIU 56%

How do I interpret the results? or interpret the result of NIU. I say some suggestions to drop NIU for CPS data. If I should drop NIU, can I use the code “where COVIDTELEW<99.” Any advice would be greatly appreciated
Thank you!

You can see who is “in-universe” for this question by looking at its Universe Page. Anyone under age 16 or not employed at the time of the final CPS interview will have a value of 99 (NIU) for this variable. Generally these people should be dropped when analyzing COVIDTELEW because they were not asked the question.