Meaning of "N/A or no schooling" in the variable EDUC (IPUMS USA)

What does the detailed code 000 “NA or no schooling” mean? We already have 001 for “NA” and 002 for “No schooling completed”. I checked my sample and found the number of observations with Educd=000 is 0 while the numbers with eudcd=001 and educd=002 are large but not equal numbers.

Besides, does the combination of educd=000, educd=001, and educd=002 (detailed codes) equal to educ=00 (general code)?

If I want to drop out all the observations that do not have a valid schooling years/ have no schooling completed, which criterion(criteria) should I use?

Here is link for the table where it occurs.IPUMS USA: descr: EDUC_section
Thank you very much!

EDUC has both general and detailed codes available. If you look at the the general codes, you will see that 00 is available (the little “X” under the year indicates availability) for all samples from 1940 onward. If you select detailed codes, you will now see that with the exception of a few years, two distinct codes are available: 001 (N/A) and 002 (No schooling completed). The code 000, in most years, is not available for the detailed codes. This allows for more detailed analysis.

When you are analyzing your extract data, EDUC will provide the general codes, while EDUCD will provide the detailed codes.

We also have some comparability notes about EDUC here, which highlights some of the differences in N/A and no schooling over time.