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.
Demographics of Singapore
After World War II, in the period from 1947 to 1957, Singapore saw a massive population increase mostly due to increased number of native births. The birth rate rose and the death rate fell; the average annual growth rate was 4.4%, of which 1% was due to immigration; Singapore experienced its highest birth rate in 1957 at 42.7 per thousand individuals. (This was also the same year the United States saw its peak birth rate.)