July $11$ is observed as

Per year growth in India's population according to the $1991$ census is (in $\%$)

According to the world population,every ...... person is an Indian.

As a country becomes industrialized,its population growth:

At the time of independence,our population was approximately ........... billion,which reached near ............ billion in the year $2000$ and crossed ........... billion in $2011$.

What is the scientific study of human populations called?