[mattmanser]

Not the working population, simply the tax revenue.

You could theoretically have one robot producing trillions of $ and tax that one robot and pay for everything.

That's one of the reasons why everyone's obsessed with growth, if the economy grows, the tax budget goes up without tax rates going up so the country can afford to pay for more stuff.

[msellout]

Good point. That's why it's likely the youth and the not-yet-born will pay a higher percent of their lifetime incomes in taxes while probably receiving less benefit. Americans have a history of voting wealth transfers to themselves from their grandchildren.