Another reason for the very low birthrate is that the welfare state renders the family unnecessary. Why have kids -- You can spend all of your money on yourself and the government will take care of you in your old age, disability, etc. On the other hand, in most of the countries of the world today, the family is still the primary, if not the only, source of welfare assistance. In these countries, if you are old or sick, and have no family to take care of you, you are in trouble.
In some countries, people still want -- and need kids. And they are reproducing.
Which is why it must be abolished.