Government intervention has sped up the process of lowering IQs in at least a couple of ways: 1) They have decimated the effectiveness of schools purposefully. 2)They have made it possible, and vigorously encouraged, idiots to procreate at much faster rates than most intelligent people choose to do. Therefore, average IQs are falling.
Along the same lines, I would add that responsible people don’t have children until they can afford it.
But it takes longer and longer to get to that point and biological clocks haven’t changed.
Even those who may want (more) children find they can’t when they are able to.