Demographic inertia The importance of age structure in determining population growth rate: all individuals are not the same.

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Demographic inertia The importance of age structure in determining population growth rate: all individuals are not the same

Demographic inertia The importance of age structure in determining population growth rate: all individuals are not the same Any individual can be placed into an age class, defined by (for example): her age her reproductive potential

An example of a “life table”

What does a life table tell you?
How long you’ll live (on average)

What does a life table tell you?
How long you’ll live (on average) When reproduction occurs (on average)

What does a life table tell you?
How long you’ll live (on average) When reproduction occurs (on average) Age structure of the population

Why should you care? The “schedule” of births and deaths determines:
the population growth rate, r the age structure the “inertia” of population growth

Demographic inertia Briefly:
An oft-stated goal of individuals who would like to stabilize the rate of population growth is the achievement of Zero Population Growth (ZPG).

Demographic inertia Briefly:
An oft-stated goal of individuals who would like to stabilize the rate of population growth is the achievement of Zero Population Growth (ZPG). ZPG is usually defined as “net replacement rate”, or 2 children per couple.

Demographic inertia Briefly:
An oft-stated goal of individuals who would like to stabilize the rate of population growth is the achievement of Zero Population Growth (ZPG). ZPG is usually defined as “net replacement rate”, or 2 children per couple. If ZPG happened tomorrow, how big would the world’s population be when it stopped growing?

Demographic inertia If ZPG happened tomorrow…
the world’s population would stop growing when it reached 9.7 billion people (or, 2.8 billion people from now). WHY?

Demographic inertia The key is the population age structure