Large U.S. banks reported negative corporate-bond inventories for the first time ever by one measure, the latest twist in a market being remade by rising investor demand and declining stockpiles at dealers that buy and sell the debt.

The figures are being closely scrutinized on Wall Street amid concerns that liquidity, reflecting the capacity to buy or sell quickly without moving market prices, has been in decline and could become more challenging as the Federal Reserve prepares for its first interest rate increase since 2006.

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