| Value | Category | Cases | |
|---|---|---|---|
| 1 | once a year | 269 |
14.1%
|
| 2 | twice a year | 48 |
2.5%
|
| 3 | every other year | 122 |
6.4%
|
| 4 | first time that was done | 1336 |
70.2%
|
| 6 | other | 129 |
6.8%
|
| Sysmiss | 36814 |