Due to herd mentality, it's unlikely that private buyers will step in until professionals put a floor on the market. It's typical bubble activity, unfortunate lemmings pile in at the top and then fear finally keeps others out as they see the disaster unfold.
OK, if we assume Bodie and Doyle step in at the right estimated yield, presumably we have all the factors we need (apart from today's ECB announcement) to establish how far prices would have to drop to make investment mathematically attractive once more. I've had a go at the calculation but I won't quote the details since I'm probably wrong... but if we assume capital appreciation is zero, I don't think even a 30% drop would be enough. Anyone better qualified like to take a guess ?