Birth rates in the developed world are below replacement levels and global fertility is not far behind. Sub-replacement fertility leads to exponentially decreasing population. Our best models of economic growth suggest that a shrinking population causes economic growth and technological progress to stop and humanity to stagnate into extinction.
One theory of fertility decline says it’s all about opportunity costs, especially for women. Rising labor productivity and expanded career opportunities for potential parents make each hour of their time and each forgone career path much more valuable. Higher income potential also makes it cheaper for parents to gain utility by using financial resources to improve their children’s quality of life compared to investing time in having more kids. Simultaneously, economic growth raises the returns to these financial investments in quality (e.g education).
In addition to higher incomes, people today have more diverse and exciting options for leisure. DINKs can go to Trader Joes and workout classes on the weekend, play video games, watch Netflix, and go on international vacations.