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The University of Southampton
Public Policy|Southampton

Understanding Recent Fertility Trends in the UK and Improving Methodologies for Fertility Forecasting


The project ‘Understanding Recent Fertility Trends in the UK and Improving Methodologies for Fertility Forecasting’ (FertilityTrends) examines the significant fluctuations in fertility levels in the UK in the last two decades, investigates their causes, and develops improved methodologies for fertility forecasting.

The last two decades have witnessed dramatic changes in fertility levels, which were not predicted by demographers or government statisticians: Fertility significantly increased in the first decade of the 21st century, whereas it has declined thereafter. These changes when translated into numbers of births, have had important implications in the provision of health services, childcare, and school places. For example, a decline in fertility levels by 10% will lead to about 40 thousand fewer newborn babies in the UK annually, and the effects may be even more pronounced locally. In the context of rapid population ageing and fluctuating migration numbers, there is an urgent need to measure the contribution of births to the growth and, even more importantly, age composition of the British population. The task of predicting short- and long-term trends in fertility presents a major challenge for social scientists, the Office for National Statistics and government departments.

We are harmonising census-linked administrative data from the ONS Longitudinal Study, Scottish Longitudinal Study, and Northern Ireland Longitudinal Study, together with survey data from the Understanding Society study. The project is thus novel in that it uses data from the all four UK constituent countries. The project will, first, produce detailed measures of fertility changes in recent years in the UK. Second, it will decompose the overall changes into those attributable to compositional changes in the UK population, e.g. by country of birth and education, and those which are attributable to behavioural changes over time, i.e. women have fewer or more children. Finally, these insights will be used to develop new methodologies for more accurate forecasting of fertility applying them to the UK and its constituent countries.

The project brings together researchers from the Universities of St Andrews and Southampton, as well as government statisticians from ONS, NRS, and NISRA, to work on an important policy-relevant topic and to improve our understanding of the factors associated with changing fertility in the UK. It will significantly improve the methodology used for fertility forecasts for the UK and its constituent countries. A better understanding of the present childbearing trends and forecast of the future developments will be critical to inform the planning of demand for various public services (e.g., nurseries, school places and housing) and the number of young people entering the workforce in the future.

Project Webpage Centre for Population Change
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