Final answer:
A population with an age structure diagram narrower at the bottom than at the top indicates a higher proportion of elderly individuals, common in developed countries with low birth rates or zero population growth.
Step-by-step explanation:
Populations with an age structure diagram that is narrower at the bottom than the top indicate a population with more elderly people than young people. This characteristic shape suggests that the population may have low birth rates and potentially a higher standard of living, which is more common in developed countries with lower population growth.
Such age structures are also associated with countries that may be experiencing zero population growth or even a decline in population size. For example, developed nations such as Italy have been observed with a more conical age structure, where the middle-aged and older populations comprise a greater percentage.