Interest rates are expected to stabilize soon or even begin falling. The risk is that core inflation might not come down, and a second tightening cycle might be needed.

Russia halted gas flows to Poland and Bulgaria, offering a foretaste of what the region might have in store.

"The ruble has ceased to be a freely convertible currency with the sweeping sanctions. In terms of currency policy, this throws Russia back to the early 1990s and the time before the country's comprehensive economic opening."

Fed and ECB strategy of moderation is fraught with risks. Still, one Fed president says, "abrupt and aggressive action can actually have a destabilizing effect on growth and price stability. The most important thing is to be measured at our pace."

FOMC did not raise interest rates in this week's meeting, suggesting 2016 will see two quarter-point increases rather than the four originally forecast.

FOMC did not raise interest rates in this week's meeting, suggesting 2016 will see two quarter-point increases rather than the four originally forecast.

The central bank may buy up to 500 billion euros of assets.

The central bank may buy up to 500 billion euros of assets.