Fertility assumptions for the 2006-based national population projections

Area of Science:

• Demography
• Population Studies
• Social Statistics

Background:

• Fertility is a critical factor in national population projections.
• Previous UK projections assumed a long-term completed family size of 1.74 children per woman.
• This assumption had been lowered multiple times in recent years.

Purpose of the Study:

• To outline the reasons behind the Office for National Statistics (ONS) decision to increase the long-term fertility assumption.
• To detail the revised fertility assumption for the 2006-based UK population projections.

Main Methods:

• Analysis of demographic trends in the UK.
• Review of factors influencing fertility rates across the four UK countries.
• Adjustment of the completed family size assumption for national population projections.

Main Results:

• The long-term completed family size assumption for the UK was raised to 1.84 children per woman for the 2006-based projections.
• This marks the first increase in the long-term fertility assumption since the 1960s baby boom.
• The revised assumption was applied across all four UK countries.

Conclusions:

• The ONS revised its long-term fertility assumption based on demographic analysis.
• The increase reflects a notable shift in fertility trends not seen for decades.
• This change impacts future UK population projections.