Answer: The larger the population the larger the increase.
Step-by-step explanation:
After the agricultural explosion of the 18th and 19th centuries, the human population grew exponentially. The thing about exponential growth is that the larger the population that is increasing, the larger the increase.
As more children were born, these children gave birth to even more children which ensured that human population doubled in little time. For instance, two people give birth to 2 children who then give birth to 2 children each - we now have 8 people. Compare this to two people giving birth to 5 children who then give birth to 4 children each.
The latter became the norm after 1850 and is why the population kept growing faster.