since humans aren't all-seeing and perfect and have flaws too, we will not always be able to see what comes next/what is going to happen. all we can do is predict and hope we're right. most of the time, we're not. like i mentioned, no one can predict the future. this doesn't apply to just human population trends, it applies to everything.
one thing humans can do to get better results is think about our growing population. humans will not die until the end of earth, so we need to think about how many people will be on this planet (how long will they be here, what birth defects can they be born with, what is more common in humans, etc.)
overall, we have about a 70% chance of being wrong and a 30% chance of being right.