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.
Developing country
Over the last few decades, global population growth has largely been driven by developing countries, which often have higher birth rates (higher fertility rate) than developed countries. According to the United Nations, family planning can help to slow population growth and decrease poverty in these countries.