私人货币与公共债务：美国稳定币与全球安全资产通道

Private money and public debt. U.S.Stablecoins and the global safe assetchannel Abstract This paper studies the international macro-financial implications of U.S. dollar-backedpayment stablecoins.These digital assets create a newglobal safe asset channel thatlinks private money creation and global payment needs directly to U.S. public debt.By reshaping the demand for safe assets and the geography of dollar intermediation,stablecoins transform the dynamics of global financial markets, generating new trade-offs, also for the U.S.:even if they widen the dollar’s global footprint and compressU.S. risk-free yields, they entail non-trivial macro-financial costs.Stablecoins dampenthe domestic real effects of U.S. monetary policy and increase both U.S. and foreignexposure to cross-country shocks, making a more digital, dollar-centric reserve systemless stable.These effects are limited at low adoption levels but rise non-linearly withstablecoin capitalization, reshaping the functioning of the international financial system. Keywords:Stablecoins, Global Safe Asset, Monetary Policy, Spillovers, Financial sta-bility JEL Codes:G15, E42, E44, E52, F3 Non-technical summary Recent technological innovation has made it possible for non-banks to issue new forms ofprivate digital money known as stablecoins. These instruments are designed to maintain astable value, typically by being backed one-to-one with safe and liquid assets such as U.S.Treasury bills. Although stablecoins originated as a tool for trading crypto-assets, theirrapid expansion and the emergence of dedicated regulatory frameworks—most notablythe U.S. GENIUS Act—have positioned them to move into mainstream domestic andespecially cross-border payments. The policy debate surrounding stablecoins is highly polarized. Supporters argue thatthey can deliver faster, cheaper and more accessible dollar liquidity across borders, po-tentially reducing frictions in international payments. Some policymakers emphasize thepotential efficiency gains of a widely available, dollar-denominated digital instrumentthat combines safety and immediacy, echoing the perspective of Waller (2025). Others,however, underline substantial risks.A first set of concerns relates to financial stabil-ity:the absence of binding prudential requirements may amplify procyclical behavior(Eichengreen et al., 2025), increase risk-taking, and entrench global dollar dominance(Rey, 2025). A second line of critique points to technological fragilities: cyber vulnera-bilities, AML/CFT, data and consumer protection and the risk of digital runs, especiallyduring periods of market stress, as emphasized in Cipollone (2025). Against this background, the transformation of stablecoins from a niche crypto toolinto a globally used form of private digital money raises an important question: Whathappens when global demand for liquidity flows directly into U.S. public debt throughprivately issued digital dollars?Under the GENIUS Act, in fact, stablecoins must befully backed by U.S. Treasury bills. As stablecoins expand, they therefore create a newchannel through which global liquidity needs and global shocks influence the U.S. Treasurymarket. We call this mechanism the global safe asset channel. When foreign users demand more stablecoins, issuers must buy more U.S. Treasurybills; when demand falls, they must sell them. As a result, the balance sheets of stable-coin issuers effectively connect global payment needs and portfolio decisions of householdsabroad with the dynamics of U.S. bond markets. This has two important implications.First, stablecoins may compress U.S. risk-free yields in the long-term, because they in-crease structural demand for short-term Treasuries. Second, changes in global demand for liquidity now translate immediately into capital flows in and out of U.S. safe assets,that may amplify macroeconomic volatility. And most importantly, these flows becomestronger, not weaker, as stablecoin adoption rises. The paper studies these mechanisms in a multi-country DSGE model in which house-holds use both money and stablecoins, issued only by the U.S., to meet liquidity needs.Stablecoins have a dual nature of both a settlement token, i.e.they are used for pay-ments, and of a trading token, i.e.dollar-denominated store of value asset.They arehowever imperfect substitutes for money because households value them less when con-fidence falls—capturing their vulnerability to runs or technological disruptions—whileissuers fully back each coin with short-term U.S. Treasuries.This setup allows us totrace how monetary policy transmission changes once stablecoins become a significantpart of global liquidity creation.The model embeds stablecoins reflecting their regula-tory design under the GENIUS Act: full backing, zero remuneration, and direct issuanceto households. Importantly, stablecoins differ from central bank digital currencies (CB-DCs) because the latter are design to avoid impacts on the demand for safe ass