| 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 | 
| Sysmiss |