Final answer:
The subject of this question is Demography, which focuses on population growth, fertility rates, mortality rates, and migration patterns. The text provides information on how these factors impact the world's population and demographics.
Step-by-step explanation:
The subject of this question is Demography, which is the study of populations, specifically focusing on population growth, fertility rates, mortality rates, and migration patterns. The information provided in the text highlights how factors such as declining birth rates, increasing life expectancy, and migration impact population trends.
According to the text, the world's population has been experiencing a decline in fertility rates and increasing life expectancy. This can be attributed to economic development, education of women, improved healthcare, and increasing urbanization. Additionally, immigration plays a role in shaping population growth and demographics.
In summary, the subject of this question is Demography. It discusses how factors like fertility rates, mortality rates, and immigration influence population trends worldwide.