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
"Secret Lives of the Super Rich"
An all-new series premiering Wednesday, Sept. 25 at 9 p.m. ET/PT. |http://superrich.cnbc.com