| Value | Category |
|---|---|
| 1 | no primary, illiterate |
| 2 | no primary, literate |
| 3 | primary |
| 4 | lower secondary (basic) |
| 5 | upper secondary |
| 6 | preliminary vocational (handicraft, industrial) |
| 7 | middle vocational (technical college, college) |
| 8 | higher (bachelor degree, master degree) |
| 9 | post-graduate |
| Sysmiss |