I think that's the point - debt is now relatively higher than at any time in history & growing exponentially. However, serviceability has also been growing at the same rate, so we can continue to afford our expensive(?) houses.
Showing debt against GDP shows some scary exponential graphs, however, plotting discretionary income growth (ie serviceability) against mortgage debt paints a realistic picture.
This is a very good point in my opinion and one which is not reflected in 'historical macro' statistics.
However its also a bit of a double edged sword.
The creation of that second income significantly increased total family discretionary income, but this is now pretty much factored into current 'prices'.
So whats the catalyst to provide the next big jump in family discretionary income?
kick the kids off to work when they are in their teens so they can help pay the mortgage??
interest rates? they have been on a decline since the 1970's (yes up and down during this time, but overall trend has been down). In the US Fed rates are zero (and the RBA got to 3%), you cant trend down much more than this.
I do note however that over time the underlying land value, especially in inner capital cities will continue to appreciate over the long term as populations increase and the land use becomes more efficient (ie subdivision).
But i can nearly guarantee you it wont be as smooth a progression as we have seen over the last 15 years.
Therefore i cannot emphasis strongly enough that risk levels will need to be set at a lower level than what could have been accomodated in the last 15yrs.
There is no point holding for the long term, if your risk level is such that you run a high probability of blowing up before you reach the 'end of your long term'.