Scottish Longitudinal Study
Development & Support Unit
Understanding Scottish birth parity – a comparison of different data
Paul Boyle (University of St Andrews)
Elspeth Graham (University of St Andrews)
Lee Williamson (University of St Andrews)
Approved on 10-11-2008 (To be submitted to PAC)
In the UK in recent years there has been a drop in the total fertility rate (TFR) along with a shift in the shape of the age-specific fertility rates (ASFR) which can be explained in the context of birth postponement. For Scotland, as in England, there has been a slight rise in fertility in the last few years, from a low TFR of 1.48 in 2002, to 1.60 in 2004, to 1.73 in 2007 (GROS 2008:22).
The ASFR and the TFR can be investigated easily using civil registration data along with Census data, but these do not explain the full fertility behaviour of women. For example, even the ASFRs do not indicate if the changes in the shape of the rates, which relate to the timing of births, are due to women changing the timing of first births or women going on to have second or third births. Thus knowledge of a women’s birth parity is key to uncovering these important aspects of fertility behaviour. Unfortunately, parity data is not readily available, since civil registration data only records all previous births within marriage, and therefore it misses a large percentage of births thus rendering the information inaccurate for generalising to all women.
Further, as to why parity fertility measures are important, Hinde (1998:118) commenting on work by Feeney & Yu (1987) describes 2 main advantages:
- First, the parity-based approach controls for past order-specific fertility. Therefore, parity-based period measures are much less prone than are age-based period measure to temporal fluctuations caused by changes in the timing of births.
- Second, fertility is coming to reflect more and more the decisions made by people about the appropriate number of children to have. Parity-based measures explicitly acknowledge this fact, whereas age-based measures do not.
There has been a limited amount of previous research into birth order and parity using the General Household Survey (GHS) by Chamberlain & Smallwood (2004). The estimates of birth order for Scotland were only for 5-year age-groups (due to small numbers in the GHS), with no geographical breakdown and for 5 year periods up until 1999 only. We hope to extend this work.
Chamberlain, J. and Smallwood, S. (2004). Estimates of true birth order for Scotland, 1945-1999. Population Trends. 117, Autumn 2004.
General Register Office for Scotland (GROS). (2008). Scotland's Population 2007: The Registrar General's Annual Review of Demographic Trends. 153rd Edition
http://www.gro-scotland.gov.uk/files1/stats/scotlands-population-2007-the-register-generals-annual-review-153rd-edition/scotlands-population-2007-the-register-generals-annual-review-153rd-edition.pdf [accessed 26-09-13]
Hinde, A. (1998). Demographic Methods. Arnold, London.