If there was any confusion where the funding for what little shopping spree Americans engaged in during December, it should all go away now. While the street was expecting a 0.2% increase in both personal income and personal spending in the month of December, what it got instead was a flat print in income (i.e. unchanged from November) while spending (mostly for non-durable goods) spiked by 0.4% meaning there was a 0.4% funding hold that had to be filled somehow. That somehow we now know is personal savings, which tumbled from a revised 4.3% to 3.9% - the lowest since January 2013, only back then incomes would rise for the rest of the year driven by the 30% increase in the S&P "wealth effect." This time, with the Fed now tapering QE, the only way is down for both the "wealth effect" and Personal Incomes... and thus Personal spending, that majority component of US GDP.
Finally, this data means that according to the BEA in December US consumers funded some $46 billion in spending through burning down their savings. As of December 31, 2013 total personal savings left are down to $495 billion.