+**Population Decline** describes the reduction in the size of a human or animal population over time. It often results from a sustained low [Birth Rate](/wiki/birth_rate) or increased mortality, leading to an [Aging Population](/wiki/aging_population) and shifts in societal structure.
+## See also
+- [Demography](/wiki/demography)
+- [Population Growth](/wiki/population_growth)
+- [Fertility Rate](/wiki/fertility_rate)
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