| Value | Category | Cases | |
|---|---|---|---|
| 7 | 2 |
2.7%
|
|
| 9 | 1 |
1.4%
|
|
| 10 | 3 |
4.1%
|
|
| 15 | 2 |
2.7%
|
|
| 18 | 2 |
2.7%
|
|
| 20 | 4 |
5.5%
|
|
| 23 | 1 |
1.4%
|
|
| 30 | 1 |
1.4%
|
|
| 77 | Don't know | 57 |
78.1%
|
| Sysmiss | 4030 |