Quarterly data on credit unions and building societies from APRA is losing its utility, as a number of large credit unions hang out a bank shingle while retaining their mutual status.Data compiled by the Australian Prudential Regulation Authority for the year to March 2012 show a decline in assets of 11 per cent over the year and a fall in profitability for the sector.Alternative, though much more brief, data compiled by industry association Abacus put asset growth for the year at 4.9 per cent.The Abacus data covers the "customer owned" banking sector and thus excludes the listed building societies in the APRA data set.Abacus said, in a media release, that it "raised the issue of data collection previously with APRA and hoped that a more complete data set can be produced in future."Four credit unions have become banks since September last year: mecu, Queensland Teachers Credit Union, Defence Force Credit Union and Victoria Teachers Credit Union. Heritage Building Society has also become a bank.Over the same period, five credit unions have merged into other entities, while one credit union has turned into a building society.