| Value | Category |
|---|---|
| -4 | missing data |
| -3 | refused to answer |
| -2 | not applicable |
| -1 | do not know |
| 0 | none |
| 1 | 3 year diploma |
| 2 | 1 year diploma / certificate |
| 3 | vocational training |
| 4 | some university |
| 5 | completed undergraduate degree |
| 6 | some post graduate university |
| 7 | completed post graduate university |