Tom Lee of Fundstrat laid out just how much, in a note to clients on Friday.

"Households have not been buying equities generally since 2007," wrote Lee.

"This is evident on the chart on the left below. As shown, there has been a substantial liquidation of equity ownership, most notably in direct ownership of stocks."

Part of this effect may be that Americans have been burned by two serious drawdowns in the stock market since 2000.

Lee points out that since 2007 households have been a net seller of stocks, and have shrunk the amount of their financial assets in stocks by 18.6% since that time.

"This is the largest liquidation in history and surpasses the 10% liquidation during the decade from 1979 to 1989—that was the precedent decade before the massive inflows into equities in the 1990s," said Lee.

Another reason Lee pointed to is the booming corporate-buyback sector, which has been the largest net source of demand for equities since the recession.

"The largest decline has been direct ownership of stocks (down $2 trillion) and this reflects the buyback programs of US corporates," wrote Lee. "Essentially, they have been buying equity holdings from households (institutional ownership of stocks is essentially the same). The only area of purchases has been domestic equity ETFs."