Answer:
It has increased rapidly
Step-by-step explanation:
In 1950 there were around 2.5 billion people living in the world, while today that number is 7.5 billions.
In most of the developed countries the population has grown rapidly, of course among the other things because health system in those countries has developed and is still developing pretty fast.
For example United States had 150 million inhabitants and now that number has doubled - more 320 millions.