Total fertility rates, which can be defined as the average number of children born to a woman who survives her reproductive years (aged 15-49), have decreased globally by about half since 1960.
This has drastically shaped today’s global economy, but a continued decline could have much more severe long-term consequences. If the world has too many elderly dependents and not enough workers, the burden on economic growth will be difficult to overcome.
Source: http://www.visualcapitalist.com/fertility-rates-dropping-economy/