| Value | Category | Cases | |
|---|---|---|---|
| 2001 | 1 |
1%
|
|
| 2002 | 9 |
9%
|
|
| 2003 | 20 |
20%
|
|
| 2004 | 38 |
38%
|
|
| 2005 | 31 |
31%
|
|
| 9999 | 9999. Don't know | 1 |
1%
|
| Sysmiss | 899 |