This page summarises data returns in the 4 Year booklet study.
Most of the figures in the table below are based on information logged in the TEDS admin database. However, figures for 'data in the dataset' are based on the final analysis dataset itself. Discrepancies between returns and actual data arise because of logging errors, unusable data, and losses of data.
The figures shown in the table below are numbers of families (twin pairs).
| Cohort (birth year of twins): | 1994 | 1995 | 1996 | TOTAL |
|---|---|---|---|---|
| Original ONS sample | 5640 | 5710 | 5460 | 16810 |
| 4 Year booklets sent | 3991 | 4578 | 3959 | 12528 |
| 4 Year booklets returned | 2803 | 2784 | 2611 | 8198 |
| Percentage of booklets returned | 70.2% | 60.8% | 66.0% | 65.4% |
| Data in the dataset | 2789 | 2762 | 2601 | 8152 |