| Value | Category | 
|---|---|
| -9 | Don't Know | 
| -8 | Refused | 
| -5 | Not Applicable | 
| -3 | Missing | 
| 1 | Less than 3 months | 
| 2 | 3 months - less than 6 months | 
| 3 | 6 months - less than 9 months | 
| 4 | 9 months - less than 1 year | 
| 5 | 1 year - less than 3 years | 
| 6 | 3 years - less than 5 years | 
| 7 | More than 5 years | 
| Sysmiss |