What is the point of the small hole in the side of a ballpoint pen?

It helps the ink flow from pen to paper properly. When ink comes out of the plastic tube inside a pen and on to the page, it sucks air with it, creating a vacuum. Outside are will try to flood into the pen to fill this vacuum and if the pen to fill this vacuum and if the pen has only one hole (i.e. the ballpoint nib) this will make the flow of the ink inconsistent as both inrushing air and ink try to squeeze through the same gap. But if the pen has a second hole, the air can flood in through this route without disturbing the ink.