Wall Street banks are increasingly choosing to hoard their US bonds rather than sell them to the Federal Reserve as speculation grows that a slowing economy and global financial turmoil will only make them more valuable.
The world's biggest bond dealers offered an average of US$7.2 billion in Treasuries a day to the central bank last month, down 40.5 per cent from a high of US$12.1 billion in October.
The amount tendered has fallen even as the dealers almost doubled their holdings of the securities.
While the amount of marketable US government debt outstanding has risen to more than US$10.5 trillion, Treasuries are proving scarce in a world where five nations in Europe have sought bailouts, the US economy is slowing again and China is weakening.
That means interest rates on everything from mortgages to corporate bonds should remain at about record lows.