| Value | Category | Cases | |
|---|---|---|---|
| 2016 | 21 |
0.6%
|
|
| 2017 | 161 |
4.5%
|
|
| 2018 | 92 |
2.6%
|
|
| 9997 | 7 |
0.2%
|
|
| 9999 | NO RESPONSE | 18 |
0.5%
|
| Sysmiss | 3261 |
91.6%
|