value of collateral posted became highly uncertain. The Black Monday decline was, and currently remains, the biggest drop on the List of largest daily changes in the Dow Jones Industrial Average. (Saturday, December 12, 1914, is sometimes erroneously cited as the largest one-day percentage decline of the DJIA. In reality, the ostensible decline of 24.39% was created retroactively by a redefinition of the DJIA in 1916.) Federal Reserve response "[T]he response of monetary policy to the crash," according to economist Michael Mussa, "was massive, immediate and appropriate." One day after the crash, the Federal Reserve began to act as the lender of last resort to counter the crisis. Its crisis management approach included issuing a terse, decisive public pronouncement; supplying liquidity through open market operations; persuading banks to lend to securities firms; and in a few specific cases, direct action tailored to a few firms' needs. On the morning of October 20, Fed Chairman Alan Greenspan made a brief statement: "The Federal Reserve, consistent with its responsibilities as the Nation's central bank, affirmed today its readiness to serve as a source of liquidity to support the economic and financial system". Fed sources suggested that the brevity was deliberate, in order to avoid misinterpretations. This "extraordinary" announcement probably had a calming effect on markets that were facing an equally unprecedented demand for liquidity and the immediate potential for a liquidity crisis. The market rallied after that announcement, gaining around 200 points, but the rally was short-lived. By noon the gains had been erased and the slide had resumed. The Fed then acted to provide market liquidity and prevent the crisis from expanding into other markets. It immediately began injecting its reserves into the financial system via purchases on the open market. On 20 October it injected $17 billion into the banking system through the open market – an amount that was more than 25% of bank reserve balances and 7% of the monetary base of the entire nation. This rapidly pushed the federal funds rate down by 0.5%. The Fed continued its expansive open market purchases of securities for weeks. The Fed also repeatedly began these interventions an hour before the regularly scheduled time, notifying dealers of the schedule change on the evening beforehand. This was all done in a very high-profile and public manner, similar to Greenspan's initial announcement, to restore market confidence that liquidity was forthcoming. Although the Fed's