Less than 1 in 20 American households has a million dollars, but 2 in 10 Americans believe they'll become a millionaire in the next decade, according to a new AP-CNBC poll.

That's clearly undue optimism for most, but maybe less optimism than there was not all that long ago:

Even before the crisis, however, Americans tended to overestimate their chances of becoming wealthy. A 2003 Gallup poll found that 31% of Americans thought it was likely they would ever be “rich,” with the median definition of “rich” being income of $122,000 or more (though nearly a fifth said they needed at least $500,000 a year to be rich). In a fascinating research paper in 2005, titled “Is This a Great Country? Upward Mobility and the Chances for Riches in Contemporary America,” Thomas A. DiPrete found that Americans in the Gallup poll overestimated their chances of becoming rich by a factor of at least two. And that the chance of becoming rich improved the higher up the income ladder you started. Those in the middle and upper-middle (the 50th to 75th percentile) had between a 15% and 18% chance of reaching income of more than $200,000 a year. They have only a 5% to 6% chance of making more than $340,000 a year.

When we talk about "becoming a millionaire," what we're talking about is not having enough money to be lighting cigars with hundred dollar bills. We're mostly talking about retirement security:

...nearly one-third (31 percent) of U.S. residents believe they would need a minimum savings of $100,000 to $500,000 if retiring this year in order to be confident of living comfortably in retirement, and 22 percent believe the minimum is $1 million or more to retire comfortably.

I honestly don't know which is worse—that Americans have for so long been reluctant to tax the wealthy because they had unrealistic expectations of becoming wealthy themselves, or that we're in an economy crappy enough to dent that optimism. But if this economy is lemons we've been given (or had forced upon us by billionaires), the least we can do is turn that decreased optimism into the lemonade of a sustainable tax structure in which the wealthy pay their fair share.