| Value | Category | Cases | |
|---|---|---|---|
| 1 | once or more in a year | 1991 |
10.7%
|
| 2 | once in 2 years | 3986 |
21.4%
|
| 3 | once in 5 years | 6068 |
32.6%
|
| 4 | once in 10 years | 4476 |
24.1%
|
| 5 | 1154 |
6.2%
|
|
| 9 | others | 934 |
5%
|