TABLE 2.
Participation in the ANTR Surveys in the Time Period 1991–2012
| Survey 1 | Survey 2 | Survey 3 | Survey 4 | Survey 5 | Survey 6 | Survey 7* | Survey 8§ | Survey 9§ | |
|---|---|---|---|---|---|---|---|---|---|
| Year | 1991 | 1993 | 1995 | 1997 | 2000 | 2002 | 2004–2008 | 2009–2012 | 2011–2012 |
| Multiples | 3,391 | 4,234 | 3,425 | 3,232 | 4,613 | 4,530 | 5,211 (+512) | 5,334 (+3,080) | 3,684 (+1,886) |
| Siblings | 3 | 7 | 1,482 | 1,510 | 1,472 | 1,455 | 1,585 (+56) | 1,400 (+471) | 891 (+333) |
| Parents | 3,037 | 3,671 | 3,240 | 5 | 26 | 2,840 | 3,287 (+37) | 2,979 (+2,485) | 2,162 (+1,878) |
| Spouses | — | — | 1 | — | 682 | 1,462 | 961 | 824 | 619 |
| Offspring | — | — | — | — | — | — | 329 | 288 | 186 |
| Total | 6,431 | 7,912 | 8,148 | 4,747 | 6,793 | 10,287 | 11,373 (+605) | 10,825 (+6,036) | 7,542 (+4,097) |
| Response rate | 72% | 59% | 64% | 52% | 52%‡ | 44%‡ | 43%‡ | 41%‡ | 42% |
Note: The number in brackets indicates the additional number of YNTR participants that transferred to ANTR research.
*
In addition, Survey 7 was also completed by 1,800 participants in the Flemish Twin Register.
§
The data collection for this survey is ongoing.
‡
Estimated response rates, allowing for the fact that some addresses for participants may have been incorrect (see text).