Final answer:
Economically underdeveloped countries have the greatest proportion of young individuals due to higher birth rates and lower life expectancies, resulting in a youthful population compared to developed countries or regions with zero population growth.
Step-by-step explanation:
When looking for which type of country has the greatest proportion of young individuals, we should focus on the age structure of the population. The answer is economically underdeveloped countries, often referred to as developing countries. These countries typically have higher birth rates and lower life expectancies, which results in a younger population. For instance, economically underdeveloped countries usually have many more very young people and fewer old people due to various factors such as less access to healthcare, which sometimes contributes to higher mortality rates at a younger age.
In comparison, economically developed countries tend to have lower birth rates and higher life expectancies, leading to an older population and sometimes to countries with zero population growth. Europe, which consists of many economically developed countries, tends to have a lower proportion of young individuals compared to developing regions.
Core nations, also known as high-income nations, similarly have fewer middle-aged individuals and more old individuals than developing countries, indicative of the aging populations in these regions.