Cash earnings tracked sideways at National Australia Bank for a third successive quarter in June. The bank said its cash earnings were A$1.4 billion while net profit was $1.2 billion.Revenue fell around one per cent over the quarter, thanks to higher funding costs for its operation in Britain as well as lower income from markets. NAB said income from retail banking "grew strongly".NAB said the bad debt charge fell seven per cent to $524 million, but noted an increased charge in business banking.Expenses were "lower", NAB said. Staff numbers declined, though the bank did not say by how much.Cameron Clyne, the bank's chief executive, told an investor briefing that the bank would persist with its investment program (with the bank only part way through an overhaul of many core banking systems).Managing the cost line at a time of docile demand for credit is one challenge."The longer we have a subdued environment the harder it gets," Clyne said."But we have an obligation to go at productivity. And we will do it. But obviously it gets harder."On the outlook for demand for credit, Clyne said:  "We're cautious on the uptick in credit growth because we've had many false starts on that."It is more, at this point in time, the confidence impacts. Confidence has been subdued and is still pretty weak. I am not quite prepared to say the funnels are unclogging."The bank did not report its net interest margin for the quarter. Finance director Mark Joiner said quarterly measures of the NIM - a closely watched metric - "can be misleading" and that the bank will no longer report the margin on a quarterly basis.Joiner said: "Our customer margin, as defined in the March half year, was reasonably flat."He said the customer margin was "a better indicator", and unchanged from the half year.Analysts badgering for a hint that the bank's margins might improve in the fourth quarter received guarded endorsement from Joiner, who conceded that some adverse trends in the second quarter (around the UK) business may not recur.On the other hand, he reminded analysts that "you've got quite substantial headwinds from the repricing of deposits and who knows what's happening on that front."Joiner did say that NAB generated $8 billion in excess deposit growth over and above that needed to fund lending growth, another measure of the low demand for credit. While demand for credit is low NAB continues to push loan pricing to match rising funding costs."The safer our banking system becomes, the more expensive credit needs to be and we should unashamedly incorporate that into product pricing," Joiner said.