Americans' holdings of corporate equities and mutual fund shares fell to $33 trillion at the end of the second quarter, down from $42 trillion at the start of the year, according to data from the Federal Reserve. With major market indexes falling even further since early July, and the bond market adding further losses, market experts say the current wealth losses from financial markets could total $9.5 trillion to $10 trillion.

Economists say the drops could soon start rippling through the economy, adding pressure to Americans' balance sheets and possibly hurting spending, borrowing and investing. Mark Zandi, chief economist of Moody's Analytics, said the losses could reduce real GDP growth by nearly 0.2 percentage points over the coming year.