| Value |
Category |
| -4 |
missing data |
| -2 |
not applicable |
| -1 |
do not know |
| 1 |
1 year |
| 2 |
2 years |
| 3 |
3 years |
| 4 |
4 years |
Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.