In the very long run, global population will only increase very slowly.

The 20th century saw the fastest growth in known history, from 1.6 billion in 1900 to 6 billion in 2000. Such rapid growth is not sustainable.

If you are interested in the topic, a Wikipedia article of human overpopulation offers further reading.
https://en.wikipedia.org/wiki/Human_overpopulation

Global population has significant impact on the living condition of people, and economy in general. Tomas Piketty’s book, Capital in the Twenty-First Century, has a good summary of researches and statistics on the topic, in Chapter 2 Growth: Illusions and Realities.
https://www.amazon.com/Capital-Twenty-First-Century-Thomas-Piketty/dp/1491591617