The Milliman 100 Pension Funding Index, which tracks 100 of the nation's largest defined benefit pension plans, released a report showing that these plans experienced a $42 billion improvement in funded status in October. The improvement came on the heels of the second-worst financial quarter on record, in which the third-quarter pension funding deficit jumped $254 billion.

The worst quarter on record is the fourth quarter of 2008, when the financial crisis hit. With the final two months of 2011 now here, there is likely to be more scrutiny in daily changes in discount rates and investment performance as the year winds down.

For the past 11 years, Milliman has conducted an annual study of the 100 largest defined benefit pension plans sponsored by U.S. public companies. The Milliman 100 Pension Funding Index projects the funded status for pension plans included in its study, reflecting the impact of market returns and interest-rate changes on pension funded status, utilizing the actual reported asset values, liabilities and asset allocations of the companies' pension plans.