| Value |
Category |
| 0 |
Wave 1 only |
| 1 |
Waves 1-7 |
| 2 |
Waves 1-8 |
| 3 |
Waves 1-9 |
| 4 |
Waves 8-12 |
| 5 |
Waves 9-13 |
| 6 |
Waves 10-15 |
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.