Standard & Poor's has issued a bullish report on the Australian residential mortgage-backed securities market, suggesting that it is on track to have its highest level of issuance since 2008.Issuance of A$8 billion in the RMBS market so far this year is already more than 50 per cent of total issuance for 2012S&P said it expected the strong issuance levels seen in the past few months to continue for the rest of the year, pushing total RMBS issuance beyond $20 billion. More than $50 billion of RMBS was issued in 2008.S&P said it expected its ratings on outstanding RMBS to remain stable for the rest of the year. It said the collateral (mortgage pools) underlying RMBS had performed well in recent years.The big risk is that a rapid increase in the country's unemployment rate could have adverse consequences for the performance of the underlying loan portfolios."We believe that likelihood is low," S&P saidThe market has some uncertainties to contend with. Investors might be frightened off by adverse changes to global financial conditions. The prudential standard for RMBS is being revised by the Australian Prudential Regulation Authority. And there will be competition for investor support when European RMBS issuers return to the market.