Can the coordinated financial firepower of the world's leading central banks produce only minor ripples in the markets?

Questions are mounting about the effectiveness of the planned measures—the most aggressive action by the central banks since the aftermath of the September 11 attacks—announced on Wednesday by the Federal Reserve and four other central banks after money markets remain little changed in response

"There is a certain concern that the money market is not coming down," Klaus Liebscher, a member of the European Central Bank governing council, told reporters in Vienna, according to Reuters.

His colleague on the European bank, Yves Mersch, said of the joint effort, "Whether it's sufficient to restore confidence remains to be seen."

A benchmark of banks' confidence to lend, the London interbank offered rate, or Libor, has dipped only slightly since the Fed, European Central Bank, Bank of England, Bank of Canada, and Swiss National Bank announced their plans.

The ho-hum reaction of the markets, some commentators say, is a sign of how behind the curve the central banks have been.

Gillian Tett in the Financial Times wonders why the central banks are taking steps that bankers were urging them to take in August, when the credit crunch began.

"It is thus little wonder that the financial markets remain so skeptical that central banks will be able to effectively resolve the market funding woes, notwithstanding this week's statement," she writes. "This fragmented regime of central banks was clearly unable to prick the credit bubble when it was inflating over the past few years; sadly, it may now be equally unable to contain the unpleasant consequences as this bubble deflates."