1. 1 Childlessness: a further look at cohort estimates based on survey time-series data Máire Ní Bhrolcháin*, Eva Beaujouan*, and Mike Murphy** * Centre for Population Change, University of Southampton ** Department of Social Policy, London School of Economics

2. 2 Outline Where have all the children gone? Possible explanations Identifying missing own children Revised childbearing history Validation Sources of misreporting Conclusions and future work

3. 3 Where have all the children gone? Proportion childless (weighted) according to the GHS birth histories, by age and birth cohorts

4. 4 Explaining these findings Potential sources of bias migration mortality institutionalisation changing differential response rates changing item non-response change in sample design respondent fatigue? forgetting? deliberate misreporting?

5. 5 Using household data to identify own children Own children in household identified via relationship code gap of 16+ years in age Matches between birth history and own children identified Own children identified who were not declared in the fertility history

6. 6 Presence in household of own children not recorded in fertility history, by womens self-reported fertility a. by declared parity b. among childless by age

7. Revise the fertility history Merge undeclared own children into original history to generate revised fertility history [checks] Validated against sources internal and external to GHS

8. 8 Intra-cohort change in percent childless by survey year, original and revised fertility histories

9. 9 Proportion childless by age and birth cohort, revised histories. GB: cohorts 1935-39 to 1970-74, weighted

10. 10 Annual TFR based on original and revised fertility histories & vital registration. GB, 1979-2007, weighted

11. 11 % with undeclared child(ren) among self-reported childless women by age and interview mode

12. 12 Potential number of questions within FI before fertility history

13. 13 Questions in Family Information section Illustration A woman with one disrupted cohabitation + one marriage with premarital cohabitation + 2 stepchildren would have to answer 24 questions before she fills in the birth history among which 7 dates…

14. Interviewer instructions Up to 1996, interviewers instructed to code the ever had a baby question as yes without asking if this was evident from household composition and step/foster/adopted children question Instruction absent in 1998, though Ask or record on questionnaire 1998-2007 No instructions available 2000-

15. 15 Quality of GHS fertility data: implications Policy estimates of true birth order indirectly, estimates of childlessness demographic, social care study of lone parent families Research demographic research on fertility and family

16. 16 Conclusions and future directions Careful monitoring by subject specialists Need to validate survey fertility histories Laptop self-completion may *reduce* rather than improve data quality Reconsider respondent burden Fertility history sensitive? or cohabitation history? Future work: estimating childlessness imputation of births?

17. 17 Acknowledgments Analysis based on the CPC GHS time series datafile constructed in collaboration with Dr Ann Berrington and with the assistance of Mark Lyons Amos. We thank ONS and General Lifestyle Survey Branch for their help with various questions about the data.