Final answer:
The world population reached approximately 7 billion by late 2011, marking a significant increase in growth rate over historical trends. Demography studies such trends and predicts continued growth, potentially reaching over 9 billion by 2050 and 11 billion by the end of the century.
Step-by-step explanation:
By late 2011, the world population had reached about 7 billion people. This milestone signifies a remarkable growth trend, as it took just 12 years to increase by a billion people from the previous count. Such an exponential increase is historically significant; from introducing farming and a population of 5 million, humanity grew to 1 billion by around 1810. The pace of growth continued to accelerate, taking a mere century and a bit to reach 2 billion, and less than another century to add an additional 5 billion, culminating in the 7 billion mark by 2011.
Demography, the study of populations, helps us understand this growth by considering fertility, mortality, and migration - critical aspects that influence population dynamics. Despite the overall increase, certain regions experience slower growth, influenced by factors like migration and changing fertility rates. The United Nations and demographers analyze these trends to make predictions for the future. By 2050, projections indicate a potential rise to 9.4 to 9.7 billion people and possibly up to 11.2 billion by the end of the 21st century.