This could be the most important trend for 2015

Traders work the floor of the New York Stock Exchange.
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One of the primary investing trends in the post-crisis market is breaking down, providing an opportunity—at last—for stock picking to come back into vogue.

Correlation, or the tendency of asset classes to move up and down in unison, is at a more than five-year low, according to data from New York brokerage ConvergEx. High correlations have been a characteristic of the market ever since the Federal Reserve started its historically active intervention in the financial markets, in large part through a bond-buying program that swelled the central bank's balance sheet past the $4.5 trillion mark.

The program, known as quantitative easing, helped tamp down volatility and in turn led to what market participants call the "risk-on risk-off" trade, in which most stocks moved in the same direction depending on the mood of a particular day. Correlation approached almost perfect 100 percent levels at various junctures over the past few years and was at 85.4 percent as recently as November.

Now, that figure is at 58.4 percent, something that Nick Colas, chief market strategist at ConvergEx, believes marks just the beginning of a longer-term pattern.