Bond market structure has evolved rapidly in recent years as regulatory change, concern about bank capital adequacy, and the Global Financial Crisis (GFC) combined to move bond markets towards exchanges and electronic venues. ETFs facilitated these developments, helped underlying liquidity, and allowed investors to express market views in tactical and strategic asset allocation. Feedback loops between ETFs and index benchmarks broadened asset allocation choices as plain and smart beta products developed. Success in withstanding the COVID shock enhanced the status of ETFs in credit markets, which was confirmed by the Fed’s decision to include bond ETFs in its QE program. A return to market structure built around individual securities, and fragmented cash markets, is unlikely.