When the G20 said last year that multilateral development banks (MDBs) should become ‘better, bigger and more effective’, most people assumed governments and shareholders would decide how far these banks could safely expand their lending. Instead, the biggest change came from somewhere else: a private credit rating rulebook. In October 2025, S&P Global Ratings quietly changed the way it measures the financial strength of multilateral lenders. This technical update is expected to allow MDBs to lend an extra $600–800 billion.
Many treated this as a minor technical fix. In reality, it revealed something more important: who really controls the world’s public borrowing capacity. The ability of MDBs to fund climate adaptation, pandemic preparedness, or debt relief is limited not mainly by laws or politics, but by how three private rating agencies run their models. When one of them changes its assumptions, the global system’s development capacity grows or shrinks.
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