This 53 year old has it right....

[JHB]

64. You throw that $70 trillion number around pretty liberally (so to speak)...

Where does it come from? Over how much time and given what assumptions? Those details do matter.

For instance, does that number assume that medical costs (for Medicare and Medicaid) will continue to rise over the next 75 years as fast as they have over recent decades and that nothing will be done to reduce that?

Does it assume current levels of taxation? Considering that high-end tax rates (both in absolute terms and in terms of what is paid after figuring for income type and deductions) are at historic lows, there is considerable room to change that. Over how much time is this again?

Please correct me if I'm mistaken, but isn't this figures over 75 years? What was the value of the world's assets in 1937?

I'll also note the effect of higher top-end taxation on financial decision making, such as "If I'm going to have to shell out this money anyway, better to spend it on my employees who are working to grow my assets than to hand it to Uncle Sam." And those employees will pay higher taxes on the additional income. More in income taxes, FICA taxes, all a little at a time, which would bring that number down quickly.

So please provide links and a breakdown, so we can determine just how reliable or unreliable that number is.