Which trend might indicate a change in population composition due to migration?

The trend that indicates a change in population composition due to migration is the migration of skilled workers to urban areas. This phenomenon reflects how individuals move from rural regions or less developed areas to urban centers in search of better employment opportunities and living conditions. As skilled workers migrate, they contribute to a shift in the demographic structure of the urban population, often leading to an increase in the proportion of educated and skilled individuals in those areas. This can result in a diverse workforce that can drive economic growth and innovation in cities, but it may also bring challenges such as increased competition for jobs and housing.

In contrast, factors like a decrease in birth rates, an increase in the elder population, and improvements in sanitation and healthcare are often related to inherent demographic trends rather than migration patterns. Decreased birth rates can be influenced by factors such as urbanization or increased access to contraception, while an aging population is typically the result of longer life expectancies and lower birth rates over time. Improvements in sanitation and healthcare usually lead to better health outcomes, but they do not directly indicate shifts in population composition due to migration. Therefore, the migration of skilled workers to urban areas stands out as a clear indication of how migration can transform the demographic landscape.