The first six trading days of August struck a blow to pension plans sponsored by S&P 1500 companies, with the aggregate funded status decreasing by $191 billion to a funding deficit of $496 billion and an aggregate funded ratio of 73 percent as of the market close on Aug. 8. 

The data was collected by global consulting firm Mercer, which also reports that this deficit corresponds to a 10 percent reduction in just six days from Mercer's calculation of an 83 percent funded ratio as of July 31, and a 15 percent reduction from the peak funded status measured in April of 88 percent.

Pension plans are affected not only by changes in the assets they hold but also by the market value of their pension commitments – effectively a debt sponsors hold on their balance sheets.  The recent flight to quality is bad for pension plans on two counts – reducing the value of their risky assets while increasing the market value of their pension debt.