> The math works fine. What doesn't work is the productivity distribution from work done.

I don’t think you really appreciate the scale of the numbers involved. It’s hard to find good numbers for Singapore, but by 2060 the US will have 186 million workers and 95 million retirees. Let’s apply those ratios to today’s economy. That’d be about 80 million retirees. If you took the entire income of the top 1%, that works out to $25,000 per retiree. The maximum social security benefit works out to $45,000. Then the average Medicare spending per retiree is $16,000 per year. (And don’t forget, that 1%-er money is also earmarked to pay for universal healthcare and free education.)

What about immigrants? They are literally dying to get into the US and increase the worker/retiree proportion.

It’s not just a matter of having people. The main reason we care about the worker/retiree ratio is that workers generate a surplus that can be used to take care of retirees. To the extent that immigrants and their kids are able to quickly join the middle class that pays the taxes that supports retirees, then immigration helps. But that same fact limits how much you can rely on immigration to address lack of internal population growth.

(That’s why European efforts to combat their lack of population growth will fail. The US, by contrast, is far better at assimilating immigrants into the middle class and will be relatively more successful.)

> That’s why European efforts to combat their lack of population growth will fail. The US, by contrast, is far better at assimilating immigrants into the middle class and will be relatively more successful

Not sure the American Dream is still alive. The Trump administration might as well be the straw that broke the camel's back.