| Value | Category | Cases | |
|---|---|---|---|
| 1 | One season | 1 |
1.3%
|
| 2 | One year | 1 |
1.3%
|
| 3 | Two years | 2 |
2.5%
|
| 4 | Three years | 2 |
2.5%
|
| 5 | More than three years | 7 |
8.8%
|
| 6 | Unspecified | 67 |
83.8%
|
| Sysmiss | 845 |