How do you dip into something which does not exist?
Exactly.
There IS NO TRUST FUND, there is NO RESERVES.
Congress pilfered and spent all of that decades and decades ago. SoSec now, comes out of the General Fund.
Now, pay attention to what is happening in states like IL where the pension funds for teachers and government workers are BROKE - and extrapolate those things on a national scale.
I think I recall it once said that to keep bennies at 1990 levels, that the taxation on existing workers JUST for SoSec would be 80% of their gross income JUST to keep bennies at 1990 levels for the boomers when they began retiring en masse.
So it begins indeed.
Cities burn to the ground when government has to impose austerity measures to keep solvent and the people who had been paying into the ponzi scheme for all their lives are going to be mightily pissed off.