Millionaires are feeling good. Maybe too good.
The Spectrem Group's Millionaire Confidence Index, which measures the investment outlook of the wealthy, reached its highest limit in its 9½-year history. After bumping along in single digits since the recession, millionaire confidence suddenly spiked to 23.
Basically, that means millionaires—those with $1 million or more in investible assets—are poised to move some of their huge piles of cash off the sidelines and into the market. The last time the index hit 23 was when it launched in 2004.
(Read more: Six words only billionaires know)
There are three possible explanations. First, the survey was taken before the Syrian flareup or the debt ceiling or the End of Summers. Things may change for them in September.
"These levels may be difficult to maintain if the market reacts negatively to any Syria issues, the continued political debate in Washington over the government shutdown and the Fed stimulus continuation," said George Walper, president of Spectrem Group.
The second possible explanation is that the wealthy are seeing sunlight through the investment clouds better than the rest of the population. While we may see Syria, emerging-market quakes, government shutdowns and shaky consumer confidence, they see an accommodative Fed, strong housing numbers and strong auto sales.
(Read more: Richest 1% earn biggest share since Roaring '20s)
The third possible explanation is my own. My theory is that the wealthy spent so much time cavorting in the Hamptons and the South of France in August that their brains got sunburned. Now that they're back in the office, we may see a more realistic number in September.
—By CNBC's Robert Frank. Follow him on Twitter @robtfrank.
"Secret Lives of the Super Rich"
An all-new series premiering Wednesday, Sept. 25 at 9 p.m. ET/PT. |http://superrich.cnbc.com