When the population of the 0-14 age group and the 15-44 age group in a country is almost identical, the growth of population is called zero growth. This means that the number of individuals entering the reproductive age group (15-44) is equal to the number of individuals leaving this age group due to aging.

Zero population growth occurs when the birth rate equals the death rate, resulting in no net increase in population size. This can happen when the fertility rate is low and there is a balance between births and deaths.

Let's understand this concept in more detail:

1. Definition of Zero Growth:
Zero population growth refers to a situation where the number of births in a population equals the number of deaths, resulting in no overall increase or decrease in population size. It indicates a stable population size over time.

2. Factors Contributing to Zero Growth:
a. Fertility Rate: When the fertility rate (average number of children born per woman) is at replacement level, which is around 2.1, the population remains stable. This means that each woman, on average, is having enough children to replace herself and her partner in the next generation.
b. Mortality Rate: Similarly, when the mortality rate is low and individuals are living longer, the number of deaths does not significantly impact population size.

3. Age Structure and Zero Growth:
The age structure of a population plays a crucial role in determining its growth rate. When the population has a similar proportion of individuals in the reproductive age group (15-44) as in the younger age group (0-14), it indicates a balance between births and deaths. This leads to zero population growth.

4. Implications of Zero Growth:
a. Economic Implications: Zero population growth can have economic implications as it affects the labor force and dependency ratio. With an equal number of births and deaths, there is limited growth in the labor force, which may impact productivity and economic development.
b. Social Implications: Zero growth can also have social implications, such as an aging population and potential strain on healthcare and social security systems.

In conclusion, when the 0-14 and 15-44 age groups of a country's population are almost identical, it signifies zero growth. This indicates a balance between births and deaths, resulting in a stable population size over time.