What should be the right level of Margin?

An article in today's Financial Times bemoans the shrinking level of collateral and gives the impression that this would be something to be concerned about - rather than give an indication that the financial system is on the way to a more sensible future. Haircuts or Margins are still way below levels required if prudent standards would be applied. As I said from long before the 2007-2009 credit crisis they should allow for one-day moves in asset prices of as much as 30 percent.  This would of course drastically reduce the overall volume of speculative and risk positions and therefore make it much less likely that price moves of such a magnitude would happen.