Banks have maintained strong deposit inflows over the past year, despite the steady fall in interest rates. According to the latest figures from the Australian Prudential Regulation Authority, banks' deposit books grew at twice the rate of their loan portfolios over the 12 months to May.However, in recent months the gap between deposits and loan growth has narrowed.APRA banking statistics published last Friday show 0.7 per cent growth in household deposits in May (an annualised rate of 8.4 per cent). Over the 12 months to May, household deposits grew by 7.4 per cent.All the major banks have grown deposits above system over the past 12 months. ANZ's household deposit book has grown by 9.8 per cent, Westpac's by 9.4 per cent, NAB's by 8.7 per cent and Commonwealth Bank's by 7.7 per cent.Among the smaller institutions, ME Bank has continued its very strong deposit growth, with an increase of 67.9 per cent over the past 12 months. RaboDirect's household deposit book has grown by 10.9 per cent, HSBC's by seven per cent, and Bendigo and Adelaide Bank's by 6.2 per cent.APRA's figures show mortgage portfolios growing by 0.6 per cent in May (an annualised rate of 7.2 per cent). Over the 12 months to May, mortgage portfolios grew by 3.6 per cent.