The Components of Change in Population Growth Rates

Area of Science:

• Demography
• Population Studies
• Mathematical Modeling

Background:

• The standard demographic balance equation uses current rates of fertility, mortality, and migration.
• This equation fails to account for the impact of historical population trends on current population dynamics.
• Understanding historical drivers is crucial for a complete picture of population growth.

Purpose of the Study:

• To develop a novel method for decomposing historical drivers of population growth.
• To quantify the unique contributions of survival progress, migration change, and fertility decline.
• To analyze these drivers across Denmark, England and Wales, France, and the United States.

Main Methods:

• Recursive application of the variable-r method.
• Analysis of average age-specific growth rates.
• Decomposition of historical demographic factors.

Main Results:

• Survival progress primarily affects older age groups, with indirect historical effects also seen at younger ages.
• Migration significantly influences population growth in Denmark and England and Wales.
• Historical fertility decline is the most substantial factor reducing population growth rates across all studied populations.

Conclusions:

• The developed method effectively disentangles historical demographic influences on population growth.
• Fertility decline is the dominant historical driver of recent population growth reductions.
• The interplay of survival, migration, and fertility provides a comprehensive understanding of population dynamics.