But that won't jeopardize the agency's ability to pay retirees who depend on it, Millard reassured lawmakers.
The PBGC has assets of $68 billion and liabilities of $83 billion. Millard said that over the long term, a new policy of creating a more diversified portfolio of 45 percent stocks, 45 percent bonds and 10 percent in alternative investments will produce better returns that give the agency a 57 percent chance to climb out of its deficit hole within a decade.
But the stock market has taken a sharp dive this month and those losses have yet to be reflected in PBGC estimates.
At present, the PBGC investment portfolio is about 70 percent fixed income assets like Treasury bonds and 30 percent in equities. That's about the same as a year ago, when the PBGC posted a 7.2 percent gain on its investments.
"We did not make the shift yet," Millard said.
There has been considerable debate over whether to shift more agency assets into stocks.
"This long-term, more diversified strategy aims at generating better returns that provide a greater likelihood that the corporation can meet its long-term obligations," Millard said.
"I am not sold at this point," he said. "Wall Street and this country is littered with people who had game plans designed by the brightest people in the room."
Millard reminded the lawmakers that the agency "pays monthly pension benefits spread over the lifetimes of participants and beneficiaries, not as lump sums. As a result, PBGC has sufficient funds to meet its obligations for a number of years."