| Value | Category | Cases | |
|---|---|---|---|
| 1 | more than once a year | 95 |
5.1%
|
| 2 | once a year | 579 |
31.1%
|
| 3 | every three years | 98 |
5.3%
|
| 4 | first time that was done | 954 |
51.3%
|
| 6 | other | 135 |
7.3%
|
| Sysmiss | 33922 |