Final answer:
Changes in population structure in developing countries over the past 30 years are mainly due to economic development, leading to urban migration, and improvements in healthcare, increasing the elderly population.
Step-by-step explanation:
The population structure of developing or emerging countries has undergone significant changes in the last 30 years due to various factors. One of the key reasons for this change is economic development and industrialization, which have led to the creation of new job opportunities.
This phenomenon has caused a considerable migration from rural areas to urban centers, where people seek better educational and job opportunities, especially in more economically developed regions such as coastal areas.
Another pivotal factor influencing population structure changes is the shifting age distribution within these countries. As healthcare improves, resulting in lower mortality rates, the proportion of elderly in the population is expected to rise dramatically.
While most low-income countries have currently high proportions of youth and young adults, by around 2050, it's expected that there will be an increase in the ratio of elderly populations, substantially impacting the demographic landscape and the standard of living for different age groups.