In 1950, the global population was around 2.5 billion. That is a significant difference from today's 8.1 billion global population! The big changes in the last century are due to a number of reasons, including most of the world seeing a notable increase in birth rates following World War II. We know the global population in 1950 thanks in large part to work done by the United Nations Population Division which was established to monitor and analyze global population trends, including population by country.
In 1950, Africa and Asia were the two continents experiencing the most substantial population growth. This was in large part due to their transitioning from an agrarian economy to an industrialized nation, which had the big side benefit of improving general health and reducing early mortality rates. China rose to be the most populous country in the world with approximately 554 million people. India was next with an estimated 361 million people in 1950.
The Soviet Union had the third-highest global population in 1950, with an estimated 180 million people. However, this number actually reflects a serious decline from years prior as the country lost nearly ten percent of its population in World War II. Japan also lost about one million in total population from before WWII to after. In 1950, the country was home to approximately 83 million Japanese.
Europe likewise slowly recovered from the effects of World War II. Some countries like Poland, which lost a tragic 21% of its population in the war, would not see its pre-war population return for a decade or longer. In 1950, Poland had approximately 26.1 million people, Germany had 68 million people, and the United Kingdom had 50.2 million people.
In the United States, the decade following World War II offered unprecedented prosperity as Europe largely struggled to recover from the devastation of the war with American companies rising to take the place of those that had been destroyed or otherwise were in recovery and unable to enter the global market. This resulted in a major economic boom which was followed by what is commonly known as the baby boom in which returning veterans contributed to a massive surge in birth rates. In 1950, the United States population was thus 153 million, making it the fourth-most populous country in the world. By the end of the decade, that population would rise to nearly 180 million.