The funded status of the 100 largest corporate defined benefit pension plans dropped by $5 billion during March as measured by the Milliman 100 Pension Funding Index (PFI). The deficit increased to $266 billion from $261 billion at the end of February, due to both a drop in the benchmark corporate bond interest rates used to value pension liabilities and flat asset returns during March. As of March 31, the funded ratio fell to 84.0%, down from 84.3% at the end of February. Meager investment gains of 0.29% for the month kept the Milliman 100 PFI asset value at $1.399 trillion, unchanged from the end of February.