The textbook treats monetary policy as a domestic instrument with domestic objectives. A run of recent research, much of it from inside the central banking establishment itself, says that framing is broken. When the Federal Reserve moves, it does not simply tighten or loosen US financial conditions; it shifts the world real interest rate, reshapes capital flows, and constrains what every other rate-setter can deliver on output and inflation. The implication is uncomfortable: domestic mandates are being pursued with instruments that have global incidence, and almost no one is pricing that in.
The clearest statement comes from the Federal Reserve Bank of Minneapolis, whose researchers argue plainly that rate-setters do not take sufficient account of the effects of other countries' monetary policy. Javier Bianchi and Louphou Coulibaly identify the mechanism: monetary policy moves the world real rate — the global price of saving versus consuming today — and through that channel a central bank's policy affects the ability of other central banks to achieve their output and inflation stability objectives. This is not a marginal frictions story. It places spillovers inside the core transmission mechanism, not at its edges.
Through this channel, a central bank's policy affects the ability of other central banks to achieve their output and inflation stability objectives.
The size of the spillover is now measurable
What was once theoretical is becoming empirical. Marijn Bolhuis, Sonali Das and Bella Yao at the IMF have built a new dataset of monetary policy shocks using high-frequency swaps data across 29 advanced and emerging economies, and find what they describe as substantial spillovers — including, notably, from small open economies, which standard theory treats as price-takers. Separately, Mauricio Villamizar-Villegas and co-authors at the Central Bank of Colombia aggregated 330 empirical findings from 50 papers to estimate a mean effect size of policy moves on capital flows. The direction of travel in this literature is one-sided: every named contributor in the dossier points toward larger, more pervasive cross-border transmission than current frameworks assume. There is no dissenting voice here arguing spillovers are small or self-correcting.
Two refinements matter for how the spillover actually lands. Liberty Street Economics argues that household heterogeneity — the share of hand-to-mouth borrowers versus unconstrained savers — amplifies international transmission, because economies with thinner household balance sheets feel both a real-income channel and a precautionary-savings channel more acutely. The Bank of Japan, working the same problem from the opposite direction, finds that the post-2022 US tightening cycle had a smaller domestic bite than expected because the credit channel — the mechanism through which higher policy rates choke off borrowing-sensitive demand — has weakened as services have grown as a share of activity. Read together: the Fed's hikes did less at home than the model said, and potentially more abroad.
The operational consequence is the awkward one. If domestic transmission is muted and foreign transmission is amplified, then the welfare arithmetic of unilateral policy-setting shifts. The Minneapolis Fed's framing — that rate-setters under-account for foreign effects — becomes a coordination argument, not merely an academic observation. The dossier contains no quantified forecasts on whether coordination will actually emerge; the FOMC is not about to add Colombian capital flows to its reaction function. But the analytical ground is moving. The next time a Fed chair is asked whether dollar policy is the world's problem, the honest answer, on the evidence assembled here, is closer to yes than the institution has ever been willing to concede.
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