The RBNZ Financial Stability Review includes some analysis of data on household incomes and household debt, based on the recently published Household Expenditure Survey for 2007.The analysis found that compared with the 2001 and 2004 survey data, credit risk did not materially increase over the intervening years.The RBNZ said mortgage debt tends to be disproportionately held by high-income households and said loan-to-value ratios are "generally quite manageable".The study also shows there is little overlap between the segment of households most exposed to negative shocks to house prices (those with high loan-to-value ratios) and the segment most exposed to negative shocks to income or interest rates (those with high debt-service to income).The data shows that the majority of households (more than 65 percent) have no mortgage (about half of these households rent and half are mortgage-free owners).Among those with mortgages the median household mortgage debt in the lowest income group (the lowest 20 per cent of households by income) was NZ$27,000 while that in the highest income group (the top 20 per cent) was NZ$137,000.The RBNZ said that between 2001 and 2007 indebted households in the middle income group had the largest growth in mortgage debt followed by those in the second-highest income group and then the highest income group.The RBNZ said the median loan to valuation fell between 2001 and 2007, which was largely a reflection of increased property prices (though prices are now falling).