| Value | Category | Cases | |
|---|---|---|---|
| 2007 | 1 |
0.1%
|
|
| 2009 | 1 |
0.1%
|
|
| 2010 | 3 |
0.2%
|
|
| 8888 | D/K Year | 0 |
0%
|
| 9999 | N/A | 1987 |
99.7%
|
| Sysmiss | 5 |