Bill Bonner

The [Fed's] action was the second time in a year that the Fed had ventured into new territory as it struggles to push down long-term interest rates to encourage borrowing and economic growth. In a statement, the Fed said it was acting because the recovery was "disappointingly slow," and it left the door open to even more purchases of government securities next year.

The Fed is an independent body, its policy decisions separated from the political pressures of the day. But it acted with a clear understanding that the United States, like many other Western countries, seems to have taken off the table many of the options governments traditionally use to give their economies a kick, particularly deficit spending.

The Republicans regained control of the House for the first time in four years in part by attacking the stimulus plan - begun by the Bush administration and accelerated by President Obama - as a symbol of government spinning out of control, contributing to a dangerously escalating national debt.

This political reality has left Washington increasingly reliant on the Fed to take action, though its chairman, Ben S. Bernanke, has said the Fed cannot fix the problem alone.

Ordinarily the Fed's main tool for spurring economic growth is to lower short-term interest rates. But those rates are already near zero. With no more room to go, it has to find another route to stimulate demand.

While the Fed step was telegraphed to the markets in recent weeks, most experts had expected $300 billion to $500 billion in purchases of Treasury debt. Still, the pace - $75 billion a month for eight months - disappointed some investors.

..in total, the Fed will buy $850 billion to $900 billion, just about doubling the amount of Treasury debt it currently holds.