>Thats right Marcia. Because you work for a living. That put a finite limit on how much you can have because there's only one of you and you're paid for your time. Now if you'd inherited millions you could sit back back and watch your capital accrue as our economic system favours the well off more and more.
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>What about Bill Gates? Did he inherit millions or did he work for his money? Not everyone who is wealthy inherited their wealth. Some of them were smart enough to build a better mouse trap...

From the same Paul Krugman:
"But six of the 10 wealthiest Americans are already heirs rather than self-made entrepreneurs, and the children of today’s economic elite start from a position of immense privilege."

Of course entrepreneurs are making lots of money on their own- but lower marginal tax rates on the upper incomes - and other factors- have led to a higher concentration of wealth in fewer families and therefore higher estate values.
Conversely, middle income families have seen a net decrease in income - and therefore lower estate values.