Almost one dollar in 10 of the reported cash profit of Big Four banks over the coming years will never become retained earnings, a new analysis by the equity research team at Citi concludes.Citi Research argues in the analysis that "around 16 per cent of so called 'cash profits' reported over the past 3 years have not flowed into capital".  Citi also forecasts that "up to nine per cent [of] cash profits will not flow into bank's retained earnings over the period to FY15."And, it says, this "capital leakage" will constrain the growth in risk-weighted assets at the Big Four, particularly at Westpac and NAB.The Citi research updates analysis first published several months ago and represents one strand of investment community opinion regarding bank reporting practices.Citi argues there are "three major sources of capital leakage" from banks' reported profits:* adjustments required by APRA, such as capitalised software and expected losses;* "business as usual" expenses, often relating to business reorganisation; and* a range of "mark to market movements" such as "other comprehensive income" and the "foreign currency translation reserve".In the past year, the Australian Securities and Investments Commission has expressed its frustration at the use of information by many companies not prepared in accordance with the IFRS accounting standard both in financial reports and in other corporate documents.Citi says banks' "cash" numbers consistently understate price/earnings ratios and lead to valuations being "overstated by 15-20 per cent" compared with valuations based on its "regulatory adjusted profit" approach. It has not changed its existing target share prices or its recommendations, however.