What happens to population growth if fertility rates remain below replacement levels?

When fertility rates remain below replacement levels, which is generally defined as an average of approximately 2.1 children per woman, the population will not be able to replace itself over the long term. Replacement-level fertility is necessary to maintain a stable population size, factoring in mortality rates and other demographic changes.

If the fertility rate is consistently below this threshold, fewer individuals will come of age to replace those who die, leading to a gradual decline in the overall population. This decline can manifest over successive generations, as the aging population means there will be a smaller cohort of younger individuals to support the older generation. Therefore, the future population is likely to decline, which can have significant implications for the workforce and economic stability of a country.

The other options presented do not align with the established demographic trends that stem from sustained low fertility rates. For instance, population stabilization does not occur unless fertility rates are at or above replacement level. Rapid population increases are typically associated with high fertility rates, and frequent fluctuations are more characteristic of populations experiencing significant immigration or emigration rather than those solely impacted by birth rates.