Net foreign purchases of U.S. long term securities were $81 billion in September. That's down from $137 billion in August, as overseas buyers slowed their purchases of Treasury bonds.

"There seems to be a predominance of short-term thinking at the expense of long-term investing," said Commissioner Daniel Gallagher of the US Securities and Exchange Commission in a speech this week.

To see the system at work, look at auction-rate securities, a sort of long-term debt invented in the 1980s.