If there were diminishing returns to QE, then it might take a little while before we see the full impact of the reduction in the Fed's balance sheet that is currently underway, but the effect should grow over time. Turning to Australia, why did Australia come through the crisis better than many other countries? There were a number of contributing factors.
[6] Good luck certainly played a role. But the policy actions made an important contribution too. Monetary policy was eased rapidly. The Australian banking system was much less affected by the problems bedevilling banking systems in other countries (partly through good luck). This meant that the transmission of the significant easing in monetary policy to the economy worked pretty much as normal.