Two of the major ratings agencies have been tracking a rise - albeit a slight one - in arrears for Australian prime residential mortgage-backed securities.Moody's Investors Service says that the 30-plus day delinquency rate for RMBS rose to 1.53 per cent in the quarter ended 30 June 2016 - up from 1.50 per cent at 31 March 2016.For major bank issuers, the 30+ day delinquency rate increased to 1.46 per cent at 30 June 2016 from 1.44 per cent at 31 March 2016, while for regional ADIs it rose to 2.16 per cent from 2.01 per cent over the same period. In contrast, the 30-plus day delinquency rate for non-ADIs dropped to 2.72 per cent at 30 June 2016, down from 2.95 per cent at 31 March 2016.There was also an uptick in 30+ day delinquencies for Australian non-conforming RMBS during Q2 2016, with the rate increasing to 4.47 per cent at 30 June 2016 from 4.12 per cent at 31 March 2016.Likewise, Standard and Poor's Global Ratings warned late last week that the number of home loans in arrears was heading upwards, with the trend more apparent in regional Australia. This was the view reported by weighted-average Standard & Poor's Performance Index, SPIN."The upward trend in arrears has been most evident in nonmetropolitan (ie, regional) areas where arrears have increased to 1.77 per cent from 1.24 per cent over the last eight months, reflecting the greater vulnerability of regional areas to downturns in key industries or employers," S&P observed. With loans in nonmetropolitan areas comprising more than 33 per cent of total loan balances underlying Australian RMBS transactions, regional economic performance is clearly influencing the overall performance of the weighted-average Standard & Poor's Performance Index. It's not time to panic yet, though. While prime arrears are up year on year, at 1.19 per cent for home loans 30-plus days in arrears over Q2, they are still below the SPIN peak of 1.69 per cent and below the decade-long average of 1.25 per cent. On an optimistic note, S&P added that "relatively stable employment conditions and historically low interest rates will enable the majority of borrowers underlying RMBS transactions to stay on top of their mortgage repayments."Moody's too, was positive in its overall outlook. Although it predicts Australian prime RMBS delinquencies and defaults will continue to rise through the remainder of 2016, owing to Australia's below-trend nominal economic growth, "losses will remain low, because of the build-up in home equity and deleveraging," said Natsumi Matsuda, a Moody's analyst.