Birth rate
As of 2017, Niger has the highest birth rate in the world with 49.443 per thousand people. 
Japan has one of the lowest birth rates in the world with 8 per thousand people.
While in Japan there are 126 million people and in Niger 21 million, both countries had around 1 million babies born in 2016.
Birth rate
As of 2016, Japan has the third lowest crude birth rate (i.e. not allowing for the population's age distribution) in the world, with only Saint Pierre and Miquelon and Monaco having lower crude birth rates. Japan has an unbalanced population with many elderly but few young people, and this is projected to be more extreme in the future, unless there are major changes. An increasing number of Japanese people are staying unmarried: between 1980 and 2010, the percentage of the population who had never married increased from 22% to almost 30%, even as the population continued to age, and by 2035 one in four people will not marry during their childbearing years. The Japanese sociologist Masahiro Yamada coined the term "parasite singles" for unmarried adults in their late 20s and 30s who continue to live with their parents.