This is due to the law that governs the phenomenon.

It's what we said earlier about phenomena that always accelerate.
They include the law of constant acceleration.

And this is because the rate of growth is proportional
to the quantity growing.

For the population, for example, it is obvious that its
growth is proportional to the number of individuals.

With few people, few parents, we have few children;
the result is a small rate of population growth.

With many people, many parents, we have many children,
thus a high speed of growth.

A year ago, when the population was smaller than today,
the speed of the population growth was smaller.

Next year, when the population will have grown even more,
the speed will be even bigger.