Better health care and living standards leads to lower death rate. Worsening economy and planned parenthood lead to lower birth rates. As birth rates drop below death rates the elderly start outnumbering the youth, leading to a demographic or population trap. Most societies work because the youth are working with the elderly are retired. If there’s not enough workforce to support the elder, there’s an eventual collapse. Eventually the population shrinks to sustainable levels and the cycle begins all over once birth rates overtake death rates. But governments don’t let this natural cycle play out because numbers must go up forever, and instead prop up the economy with fresh immigrants to replace the unborn children their original citizens did not have. It’s a ponzi. The only true solution is to let every country’s population crash naturally or for people to give birth at a rate slightly above the death rate.