Frequency | The number | The percentage | The serial number |
1 - 3 times/year | 75 | 36% | 1 |
4 - 6 times/year | 61 | 26.1% | 2 |
7 - 10 times/year | 38 | 7% | 5 |
10 times more/year | 46 | 10% | 4 |
Not sure | 57 | 20.9% | 3 |