Reserve Bank of Australia financial stability chief Luci Ellis presented new evidence yesterday supporting the RBA's claim that Australia's housing prices are not yet an asset bubble.In a speech to a Finsia financial services conference, Ellis argued that far from being complacent about a bubble, the RBA was searching for danger signs.But, she said, it was important to go beyond statistical averages to understand the housing market. As an example, she set out new detailed data on housing loans suggesting that loan-to-valuation ratios are rising because there are fewer low-ratio loans, not because there are more high-ratio ones (see graph).Ellis argued that simple ratios based on average data had wrongly led some observers to conclude, in the mid-2000s, that the US was less likely to have a housing price bubble than many other countries. In fact, while the average US borrower was safe, one group of US borrowers was taking out loans they could not pay back.Prudential supervisors needed to see "the concentrations of risk, not just what is happening on average," she said.The need to see concentrations of risk meant financial institutions would need to report more information to regulators, she added.The RBA has walked a careful line on the housing market. It has argued that current consumer leverage does not warrant any anti-bubble action. Dr Ellis has been attacked in some forums for her May 2010 comment that we "do not have a credit-fuelled speculative boom on our hands". At the same time, the RBA has also warned that greater consumer borrowing could demand action.In her speech, Dr Ellis also addressed concerns similar to those voiced in Banking Day by Professor Ian Harper about the need for a close relationship between the RBA and APRA on prudential supervision. She argued that the existing relationship was strong, and that it was based on more than just the relationships established by current APRA officials during their earlier RBA careers.