The number of Australian properties being mortgaged is climbing, although overall values are increasing faster than outstanding debt. This is one reassuring message from CoreLogic research analyst Cameron Kusher after crunching through the Australian Bureau of Statistics residential property prices indexes for the March 2017 quarter.These numbers were released earlier this week, allowing Kusher to then compare the ABS data set - covering the value of dwelling stock and the number of residential dwellings - with the Australian Prudential Regulation Authority's data on outstanding mortgages. Based on these two datasets, 58.4 per cent of total housing stock was mortgaged to Australia's authorised deposit-taking institutions, as at the end of the March 2017 quarter. This was up from 57.5 per cent a year earlier and from 50.0 per cent five years earlier.  The data highlights the proportion of dwellings that have a mortgage to a local ADI has been increasing. However, a sizeable proportion of total housing stock is not an exposure for a local ADI, as some of these properties will be subject to mortgages with non-ADIs and some may also have mortgages to offshore banks, "although the overall proportion in these two categories is likely to be quite low," Kusher said.His analysis also showed that the total value of residential housing is substantially higher than the value of outstanding mortgage debt.  In March 2017, 22.6 per cent of the total value of housing nationally was outstanding to a domestic ADI.  Kusher conceded, though, that his analysis is potentially biased by those home owners that have no housing debt. "Recent buyers in particular will in most instances be in nowhere near as strong a position as this indicates, nor will those that purchased at the peak of a market which has since undergone a correction," he wrote. Over a given year the volume of stock which actually sells is a small proportion of total housing stock (under five per cent in the 12 months analysed by CoreLogic, slightly more in peak times).  "Although an increasing number of households have taken on housing debt, the value of that debt is rising at a slower pace than the value of housing which is reducing the level of leverage across the market (at a macro level)," noted Kusher.  In separate analysis, Moody's Investors Service says that its downgrade of Australian banks has a very limited impact on securitisation transactions and covered bonds in Australia, and although housing market risks remain negative, any losses will stay low.