| Value | Category | Cases | |
|---|---|---|---|
| 1 | once or more in a year | 832 |
14.1%
|
| 2 | once in 2 years | 1134 |
19.2%
|
| 3 | once in 5 years | 1777 |
30.1%
|
| 4 | once in 10 years | 1251 |
21.2%
|
| 5 | not known | 517 |
8.8%
|
| 9 | others | 390 |
6.6%
|