Population of the world

WHICH ARE THE MOST DENSELY POPULATED REGIONS IN THE WORLD? Why?
The regions that are localized in the northern emisphere, bacause is a temperate zone, especially between 20º and 50º latitude North.

WHICH ARE THE MOST DENSELY POPULATED COUNTRIES? Is all territory densely populated.
China, India and Japan, have about 2,500 million people, almost 40% of the world's population.