One way to judge the best performing bank share over the last twelve months might be to select the one that has lost the least value.Westpac shares have lost 30 per cent of their value since peaking at $31.32, closing yesterday at $22, with merger partner St George, supported by the takeover premium, down 26 per cent since peaking to $28.59.Commonwealth has dropped 36 per cent from highs to $40.08.Australia and New Zealand has slumped 51 per cent to $15.45, with National the worst major bank performer losing 56 per cent of value to $19.60.Investment banks have been the hardest hit, with Macquarie value falling 69 per cent since trading as Macquarie Group, to $26.05, with 40 per cent wiped off the market capitalisation in the past six trading days.Babcock & Brown is a mere shadow of its former self, with a closing price of just 76 cents yesterday representing a 98 per cent loss of value.Regional banks have fared reasonably on the scale of banks overall, with Bank of Queensland down 32 per cent to $13.27, and Bendigo down 39 per cent to $10.52.Suncorp has been battered, with the value falling 61 per cent to $8.35, after an extraordinary recovery yesterday, as shares traded at intraday lows of $7.15.AMP is down 42 per cent to $6.31.When falls are viewed since September 10, six trading days ago, National is down 22 per cent, Australia and New Zealand twelve per cent, Westpac nine per cent, Commonwealth eight per cent and St George ten per cent.Suncorp is down 21 per cent, AMP 15 per cent, Bank of Queensland 13 per cent and Bendigo eight per cent.