1. Post-World War II Baby Boom: After the end of World War II in 1945, many countries experienced a significant increase in birth rates, leading to a surge in population growth.
2. Improved Healthcare: Advances in medicine, public health, and sanitation contributed to a decline in mortality rates, especially in developing countries. People lived longer, and more children survived to adulthood.
3. Economic Development: Rising living standards and improved access to resources like food and clean water supported population growth. Industrialization, urbanization, and agricultural advancements increased the ability to sustain larger populations.
4. Demographic Momentum: Populations have a built-in momentum due to the existing age structure. Even if birth rates decline, if there is a significant number of people in reproductive age, the population can continue to grow for some time.
As a result of these factors, the global population more than doubled during this 40-year period. In 1950, the world's population was approximately 2.5 billion, and by 1990, it had reached over 5.2 billion. This rapid population growth had profound impacts on societies, economies, and the environment, shaping the world as we know it today.