Not sure how "historic" these current lows are. In the 2006-ish to 2009-ish years, rates were lower and even negative:
In 2006, the national personal savings rate calculated by the U.S. Department of Commerce was around negative 1%. It was the second straight year that the measure indicated Americans are spending all of their after-tax dollars and then some. In 2005, the savings rate was negative 0.4%.
-- Is the Negative Savings Rate A Negative for the Economy? (Wall Street Journal, July 12, 2007)
EDIT: wow that article is a fun little time capsule:
While negative rates of saving are not sustainable in the long-term, they do not signal financial stress for U.S. households. Nor are they an early warning of "hard landing" of the U.S. economy.
This was written 14 months before the entire global financial system almost collapsed in Fall 2008)