Why does japan have a larger population?

Japan's high population is probably a result of:

1) High growth rates during the late 19th and early 20th century.

2) Ethnic Homogeneity.

3) A higher standard of living (about 90% are considered middle class) resulting in longer life expectancies (about 80 yrs old).

However, within the last year or two Japan has experienced:

1) Falling birth rates

2) Almost no net immigrations

Japan is the tenth largest country in the world by population. China is the most populated. Hope this helps.