| Value | Category |
|---|---|
| -9 | don't know |
| -8 | refused |
| 1 | possible to achieve without much effort |
| 2 | possible to achieve with some effort |
| 3 | possible to achieve with normal amount of effort |
| 4 | possible to achieve with more than normal effort |
| 5 | only possible to achieve with extraordinary effort |
| Sysmiss |