Dropping fertility rates can lead to shrinking populations and a higher ratio of the elderly to working adults—which will have unwanted economic consequences like increased healthcare costs and a reduced tax base.
Short-term solutions like immigration can help until populations are shrinking in every country. Longer-term solutions—reducing the cost of raising a child, and providing better support for families with children—are common strategies deployed to ward off demographic disaster.
The current crop of humanity has never had to contend with shrinking populations on a global scale. How will this reshape human livelihoods, priorities and expectations from life? We might soon find out.