This just pushes the question further away: What difference does it make if the average age of the population is 35 years instead of 45 years?
Discussion
The balance between producers and consumers in society, basically. Imagine a fishing village with 99 people too old to go out and fish, and 1 person who could. Obviously these imbalances correct themselves, eventually, but the transition can be unpleasant.
This is the mal-investment the US should be most concerned about.
We have created an industry of financial derivative jobs that are not productive to human progress.
Productive jobs should be incentivized.