Recent U.S. economic data do not seem bad enough to push down share prices this much, but the fall seems unstoppable.
One reason is that repeated corporate accounting scandals have hurt investor trust. People feel they can't rely on U.S. firms' earnings reports.
During the information technology bubble of the late 1990s, corporate managers forged brisk earnings by cooking their books. Accountants not only failed to fulfill their duties but may have been involved in wrongdoing.