There is a problem with supporting the large number of retirees that can be seen in this graph.
Keep in mind that these are official figures, that assume anyone 15 to 65 is a productive worker, and people 0-14 and over 65 are supported by the economy. A more realistic graph would start at 25 instead of 15, and have the USA’s support ratio around 3 now. The idea that 15 year olds are working and earning a living is a holdover from 100 years ago, but these are the official figures.