Over the last century, how has the global population trend been characterized?

The characterization of the global population trend over the last century is best described by the observation that the population has been growing, even as fertility rates have been declining. This phenomenon can be attributed to several factors.

Firstly, advancements in healthcare and technology have led to lower mortality rates, particularly in childbirth and for children. As health improves and life expectancy increases, more individuals live longer lives, contributing to overall population growth.

Secondly, the concept of demographic transition plays a significant role. Many countries have moved through different stages of demographic transition, where initially high birth and death rates give way to lower death rates while birth rates take longer to decrease. As a result, there can be significant population growth during the transition phase, despite a decline in fertility rates.

Furthermore, while some regions have experienced more significant drops in fertility rates than others, the global population momentum—where the large base of younger individuals leads to a growth in the number of people even as families have fewer children—supports this trend.

The other choices do not accurately reflect the overarching trend of global population growth in relation to fertility rates.