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A senator with nothing left to lose politically is betting $1.5 trillion on the stock market to save Social Security. Sen. Bill Cassidy (R-La.), who lost his primary earlier this year and leaves office in January 2027, wants to skip the usual fight over raising taxes or cutting benefits entirely. His plan borrows money and invests it instead, an approach no other lawmaker has put on the table.
The mechanics are straightforward. The federal government would borrow $300 billion a year for five years, totaling $1.5 trillion, and place it in a fund separate from Social Security’s trust fund. That money would go into stocks and other assets, modeled after the National Railroad Retirement Investment Trust, created in 2001 to let railroad pensions invest in private securities.
Cassidy estimates the fund could grow over 65 to 70 years to cover 60% to 65% of Social Security’s unfunded liability. He argues the borrowing wouldn’t add to the national debt since the money would sit in a government-held escrow account the entire time. Economists who’ve run the numbers on that assumption reach a very different conclusion.
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Boston College Researchers Found the Plan Fails Two Out of Three Times
The Center for Retirement Research at Boston College ran 10,000 simulations to test Cassidy’s math. Using the plan’s own optimistic 6.5% real return assumption, the fund fully repaid its borrowing only 36% of the time. Using return estimates closer to what many economists expect today, the success rate dropped to just 19%.
The American Enterprise Institute reached a similar verdict. Scholar Andrew Biggs ran more than 1,000 stress tests using the plan’s assumed 8.9% return, then compared it against the Social Security Administration’s own more conservative 8.2% estimate. His conclusion: roughly a 30% chance the fund pays for itself, a number that tracks closely with what Boston College found independently.
CRR senior advisor Alicia Munnell called the proposal a “flight of fancy” in an April commentary. Her critique centers on precedent: the Railroad Retirement Trust and Canada’s Pension Plan both invest tax revenue and employee contributions already collected, not money borrowed against future returns. That distinction changes the entire risk calculation Cassidy is asking Congress to accept.
The Real Borrowing Figure Could Reach $26.6 Trillion, Not $1.5 Trillion
The $1.5 trillion headline number understates what the plan actually requires. CRR researchers calculate the government would need roughly $25.1 trillion in additional borrowing to cover Social Security’s benefit gaps while the investment fund grows, pushing total new debt closer to $26.6 trillion over 75 years. History offers a warning about betting borrowed money on markets.
Illinois tried a version of this in the 2000s, issuing pension obligation bonds and investing the proceeds to close its pension gap. Investment returns fell below borrowing costs, leaving state finances weaker than before. Cassidy points instead to the Railroad Retirement Trust’s strong returns since 2001, though that fund invested payroll taxes already in hand, not borrowed capital.
Cassidy finished third in Louisiana’s GOP primary in May with 24.8% of the vote, beaten by a Trump-backed rival. His Senate term expires January 3, 2027. Co-sponsor Sen. Tim Kaine (D-Va.) shares ownership of the plan, but Cassidy has said he’s already asking colleagues to “carry the torch” into the next Congress if this one won’t act.
Retirees See No Change Yet, But the 2032 Deadline Isn’t Moving
Social Security’s Old-Age and Survivors trust fund is projected to run dry in 2032. After that, incoming payroll taxes would cover about 78% of scheduled benefits, an automatic 22% cut unless Congress intervenes. Current retirees wouldn’t notice any difference under Cassidy’s plan in the meantime; the fund would need decades to grow before it could help.
Congress remains split on whether to act at all. Sen. Josh Hawley (R-Mo.) has said reform proposals usually amount to code for cuts, while Speaker Mike Johnson has pushed Republicans to tackle the issue if they hold Congress in 2027. No formal legislation for Cassidy’s plan has been introduced. It remains a policy outline, not a bill.
Cassidy’s proposal doesn’t eliminate the sacrifice Social Security’s shortfall demands. It relocates the sacrifice to financial markets, gambling seven decades of stock returns against a debt no one can walk away from if the bet fails. Every fix on the table asks someone to absorb risk. This plan simply asks the market to absorb it first.