What countries stayed, respectively, the first and second most heavily populated throughout the 20th century?

China and India were and remained #1 and #2 in population throughout the 20th century. In 1900, China had a population of 400 million people. By 2000, China's population had reached 1.3 billion. India's population in 1900 was around 250 million, and by 2000 had grown to 1.05 billion. For comparison sake, the United States' population in 1900 was 75 million and in 2000 the US population stood at 282 million. The population in India and China not only started the century higher than other nations, but grew at a faster rate. (Population figures can be found at Our World in Data.)

The countries that remained, respectively, the first and second most populated throughout the twentieth century were China and India.

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.

The comparison between Portuguese and Dutch trade in Asia is done below

Explanation:

Dutch

Monopoly of spice tradepossessed  trading post empiresLater practiced colonial form of domination instead of trading post empiresAttention geared towards Indonesia Attempt to control the shipping business

Portuguese

Unrest in trade due to less value placed on European trade goodsRaiding of ships and getting away it in order to circumvent monopolistic behaviorsThe Muslims who were monopolistic in spice trade thru setting up of post empires and seizing it force.