If a change in margin requirements were taken by investors as a signal that the central bank would soon tighten monetary policy enough to burst a bubble, then there might be the appearance of a causal effect. But it is the prospect of monetary policy action, not the margin increase, that should be viewed as the trigger.
On the other hand, some more optimistic points were made: for example, the banking sector is in much better shape now than before the last recession. What we didn’t discuss, but in my view is crucial to the euro area’s shock-absorbing capacity, are private risk-sharing channels. Here the discussion about the capital markets union is very important.