If it's not infinite then it has to be zero sum whether it's growing or not.
The US economy generates about $16 trillion in income a year. The net worth of households and non-profits is about $55 trillion. That's a really big, finite number. If 600 families control the vast majority of that wealth then that leaves less for everyone else. And if those 600 families are able to increase their share, which they have been, then less and less will be left over.
That sounds like zero sum to me.
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It's funny, when the discussion is about transfer of wealth to the upper class, the economy is not a zero sum game. The rich people aren't taking slices of pizza from everybody else, they're just making a whole 'nother pizza for themselves.
But when the discussion is about welfare and health insurance being subsidized by the government, THE POOR ARE STEALING DIRECTLY FROM THE RICH OH MY GOD HOW CAN YOU SUPPORT STATE SANCTIONED THEFT
The argument would be, is the rich getting their money voluntarily? if i get paid $25 for mowing a loan, i don't consider the $25 the government's money that they loaned me so they can take any or all of it if they want.
No, that's not anywhere near the argument.