The plunge in oil prices to five-year lows shows that the 2008 financial crisis is still having an impact, says Christopher Whalen, senior managing director and head of research at Kroll Bond Rating Agency.

"In many respects, the sharp drop in the value of oil is just another aftershock from the financial bust of 2008, a reflexive adjustment by markets to changes in demand for key commodities," he writes in The National Interest.

"As much as we'd all like to believe that the years of grinding adjustment since the sub-prime crisis are over, the precipitous decline of oil prices shows that the healing process is still underway."

Over the past six years, central banks have sought to avoid asset price deflation and debt reduction, "two necessary components of the economic healing process which must inevitably follow any credit bubble," Whalen notes.

Now falling commodity prices are igniting deflation, he writes. "While the Federal Reserve and other monetary authorities have targeted a 2 percent annual inflation rate, it is pretty clear that deflation remains the dominant theme in the global economy for 2015."

U.S. consumer prices rose just 1.4 percent in the 12 months through November.

Many economists celebrated that statistic, as it reflected a sharp drop in gasoline prices in recent weeks. "The consumer is getting a well-deserved break," Stuart Hoffman, chief economist at PNC Financial Services Group, tells Bloomberg.

"We're seeing a little more wage growth, more jobs, better confidence and finally a price break at the pump. It adds up to a very strong holiday season."

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