This would be true except the SS tax ceiling is extremely low. SS does not scale on the rich past $128,400.
One man owning 10 robots will pay less SS than 10 workers.
This is the whole reason why the "crisis" of SS is vastly overstated and a political choice, given the obvious available solutions.
That can be changed. The difficulty is more related to corruption and lobbying than any economical constrain.
But, you are right. If nothing changes on how taxes are collected, or if it continues changing against social wellfare then it is a problem.
You could structure social security as a tax on capital, but that isn't how it currently works.
Yes. 100% true. I just mean that it can be changed. It is not an economic constraint, but it is the current situation.
It's absolutely tied to population.
[0] https://tradingeconomics.com/united-states/employed-persons
Social Security works with economic growth. It doesn't matter if you get 10 babies or 10 robots. Automation makes possible to keep proper living standards without exponential population growth.
Social Security, as other services like education, stops working because it is not shared.
Actually, with enough automation, it is easier to satisfy a smaller population.
There are 3.5 million professional truck drivers in the United States. Self-driving trucks mean that you need 3.5 million fewer babies to carry out that task. Just 3 million if you actually need 500,000 people to maintain the software.
So, I agree with you that in the past Social Security was depending on population growth. That has been changing fast for the past 50 years. There is no economical reason to not have Social Security in the future.