Final answer:
To keep a population stable, the average woman would need to have a fertility rate of about 2.1 children, which is slightly above the number 2 to account for those who may not reproduce. Countries with a fertility rate lower than this are experiencing population declines unless immigration compensates for the deficit.
Step-by-step explanation:
In order to keep the population of a country from fluctuating, the average woman would need to have a fertility rate of about 2.1 children. This number, slightly above 2, accounts for the fact that not all children will reach reproductive age or have children of their own, hence it's referred to as the replacement level. Countries like Japan, Spain, Russia, and others mentioned have fertility rates below this level, indicating a population in decline unless offset by immigration. Urbanization, industrialization, laws like the one-child policy in China, and other factors can influence a country's fertility rate.
High infant mortality rates and differences between the number of children born and the number raised in the same household can also affect the fertility rate. An average fertility rate of 1.5 children in a country like Russia indicates a declining population, not sufficient to maintain the replacement level. Similarly, Spain and Italy's fertility rates of around 1.2 are significantly below the replacement rate. However, factors such as demographic profiles, life expectancies, and societal trends play a crucial role in the actual population growth or decline.