| Value | Category | 
|---|---|
| -2 | na | 
| -1 | missing | 
| 1 | some primary | 
| 2 | primary school graduates | 
| 3 | some junior high | 
| 4 | junior high school graduates | 
| 5 | some high school | 
| 6 | some vocational school | 
| 7 | high school graduates | 
| 8 | vocational school graduates | 
| 9 | some university | 
| 10 | university graduates | 
| 11 | above university | 
| Sysmiss |