Fertility and desired fertility: Longitudinal evidence from Thailand

Summary

The validity and usefulness of ‘desired additional children’ and ‘ideal family size’ as predictors of fertility are analysed in this paper on the basis of longitudinal survey data from Thailand. First, the extent of measurement error in these variables is considered, and it is concluded that the error variance and the true variance are of similar orders of magnitude. Secondly, the changes in attitudes subsequent to births and deaths of children are investigated. It is found that the number of additional children desired is decreased by births and increased by deaths, but less than would be expected if ‘desired additional children’ represented an unchanging target family size. ‘Ideal family size’ is almost unaffected by births and deaths. Thirdly, the contribution of attitudinal variables to behavioural models is examined. It is found that desired fertility is explained no better than fertility in a standard economic model. A birth function separating desired children from identifiable physiological factors as explanatory variables indicated that the former was just significant. A model of contraceptive acceptance also found desired fertility to be a significant determinant. Thus, desired fertility can be successfully integrated into behavioural models. But on the whole, its explanatory power was weak, and it was concluded that the independent use of this variable does not significantly improve on models which relate fertility to socio-economic variables directly.

Additional information

Notes on contributors

G. B. Rodgers

This paper arises out of a joint project of the International Labour Organisation and the Institute of Population Studies, Chulalongkorn University, Bangkok. It is based on data collected by the Institute of Population Studies. The collaboration of Thienchay Kiranandana in this work is gratefully acknowledged. Helpful comments and suggestions were provided at various times by René Wéry, Richard Anker, John Knodel, Warren Robinson, T. Paul Schultz, Peter Peek and Mike Hopkins. However, neither they, the ILO, nor the IPS take responsibility for views expressed in this article.