Answer:
The countries that remained, respectively, the first and second most populated throughout the twentieth century were China and India.
Step-by-step explanation:
In 1950, China was the most populous country and owned more than 20% of the world's population. In second place came India, followed by the United States (USA), Russia and Japan in fifth place. Brazil was in eighth place. Before the largest country in Latin America was Germany and beyond came three other Western European countries: England, Italy and France.
By 2010 the picture had changed a lot. China continued in the first place, but with just under 20% of the world's population. India came together and approached the size of the Chinese population. The US continued in third place. Indonesia moved to fourth place and Brazil to fifth place. Germany fell from seventh to fifteenth, while the other European countries - England, France, Italy, Ukraine and Poland - were off the list. Russia fell from fourth to ninth, while Japan fell from fifth to tenth. Highlights were Pakistan, Nigeria and Bangladesh.