To solve birth rates, governments could give newlyweds loans to buy a home. 25% of the debt could be cancelled upon birth of each child. The loan would require the mother to stay at home to raise the children, thereby lowering male unemployment. Exceptions could be made if the father was unemployed. From there, you could also have a 6% income tax on unmarried men 25-50, and unmarried women 20-45. Monks can be exempted.