The board responsible for administering the federal government’s 401(k)-style retirement savings program on Wednesday reaffirmed a 2017 decision to expand the Thrift Savings Plan’s international (I) fund to include a broader array of foreign investments, defying pressure from a bipartisan group of senators.

In 2017, the Federal Retirement Thrift Investment Board voted unanimously to change the index upon which the I Fund is based, from the MSCI Europe, Australasia and Far East Index to the MSCI All Country World Ex-US Investable Market Index, beginning sometime next year. The move marks a shift from a predominantly Euro-centric index, along with Japan, Hong Kong, Australia and New Zealand, to investments in 48 markets around the world, most notably including Canada and China.

But in August, Sens. Marco Rubio, R-Fla., and Jeanne Shaheen, D-N.H., sent a letter to the agency, urging officials to reverse the decision, citing the Chinese government’s history of human rights abuses and other national security concerns. The senators were joined by Sens. Mitt Romney, R-Utah; Kirsten Gillibrand, D-N.Y.; Josh Hawley, R-Mo.; and Rick Scott, R-Fla., in a second letter last month.

At a meeting of the TSP board last month, consultants from Aon Hewitt, who originally recommended moving to the broader index in 2017, reaffirmed their recommendation, noting that the new index more accurately matches the statutory language establishing the I Fund and that it is forecast to perform significantly better in the coming decades than the existing benchmark.

Last week, Rubio and Shaheen introduced a bill (S. 2791) that would block the TSP from investing participants’ funds in Chinese markets. But at a meeting Wednesday, the TSP board reaffirmed its original decision, citing its fiduciary responsibility to participants and beneficiaries and noting that the law establishing the TSP is intended to shield the agency from political pressures.

“The legislative history is quite dense, but when drafting the statute, Congress discussed the fact that, unlike a defined benefit program, the funds [in the TSP] would remain the property of the account holders, not the federal government,” said TSP general counsel Megan Grumbine. “They also worried that as the fund grew, it could be the subject of even more pressure . . . Now, the board does take advice from another body, but that’s the Employee Thrift Advisory Council.”

ETAC Chairman Clifford Bailey said that both the council members and their constituencies have discussed the controversy over broadening the I Fund index, and that they developed a consensus that federal employees should have the same 401(k)-style investment opportunities as their private sector counterparts. All 10 of the largest publicly traded U.S. companies include access to the Chinese investment market in their 401(k) packages, and the same is true for the 10 top awarded federal contractors, as well as the 20 largest public sector pension programs.

“Our group said, ‘I’d like to have that option, not withstanding political issues and the reasons presented by the senators,' ” Bailey said. “Leave it up to individual participants to have the options to invest how they choose, based on their beliefs and opinions. They just want the same options as those in the private sector.”

TSP Board Member Dana Bilyeu said that although there may be merit to the idea that Americans should not be invested in some Chinese companies, that’s a matter for a different government organization to decide.

“The Treasury Department’s Office of Foreign Asset Control is the arbiter of the investible universe, of what international securities are available to be invested in in the U.S.,” Bilyeu said. “The foreign asset control list—that’s the screen that’s applied to all investments available to Americans . . . It seems to me that this is a good conversation to have, but the right people to have that conversation [are officials at the Office of Foreign Asset Control] . . . Then it would apply to all U.S. investors, not just a subset of those who happen to be employed by the federal government.”

Ron McCray, also a board member, said that if anything, the case for moving to the broader I Fund index has strengthened within the last two years, not diminished.

“In my view, that decision is faithful to the authority granted to us by Congress, and it’s in the best interest of our beneficiaries and participants,” McCray said. “I’m unaware of any fact that has come to the fore that changes any of those conclusions regarding our authority, responsibilities or what’s in the best interest of the plan’s beneficiaries. If anything, our case is stronger today than it was in 2017.”

Bill Jasien was the lone dissenter on the TSP board. He argued that the TSP should “pause” for 12 to 18 months and lobby Congress to change the law to allow both the existing I Fund as well as an optional “emerging markets” fund, which could include Chinese investments.

“If we were adding this as an option, I’d be fully supportive, but we’re talking about mapping an existing set of participants [onto a new index],” Jasien said. “We know how important international exposure is to a well-rounded portfolio, and participants would have to understand that and then make a concerted effort to reallocate their funds. And they’d end up excluded from having international exposure as a consequence.”

Board Chairman Michael Kennedy said the senators’ demands are simply outside the purview of what the TSP board is supposed to consider.

“When I think about it, this all goes back to the role of the board in terms of what we’re responsible for as fiduciaries,” he said. “Congress was very intentional in providing guard rails around this so that we as a board make decisions solely for our beneficiaries and participants. Over the years, people have talked about adding funds based on [environmental, social and governance principles] and other things, but we’ve always maintained our focus on Ps and Bs.”