Westpac chief executive David Morgan spent a good part of yesterday's 2007 results briefing arguing that the bank's strong performance in the year to September was repeatable. He needed to; there were a number of aspects of the result that looked like one-offs and windfalls, and there were other aspects that looked as though they would have an increasingly negative impact on performance.The 23 per cent increase in cash earnings for the wealth management division, BT Financial Group, was due, in part, to an acceleration of superannuation contributions that resulted from post-June 30 changes to contribution limits and tax rules. June 30 next year could be the hangover after the party.The 16 per cent increase in earnings for Westpac Institutional Bank was helped by the liquidity crisis in the global credit markets. Corporates flocked back to their banks to borrow money after credit investors closed their doors in August. WIB boss Phil Chronican said the demand for funds was such that his team had to "regulate the flow".Another benefit was that for the first time in years corporate customers paid close attention to their interest rate and currency risk; WIB's market operations were kept busy hedging on behalf of anxious clients. It is unlikely that the global credit market will still be in the same volatile state 12 months from nowIn the meantime the bank is facing a blow-out in bad debts in New Zealand (though incurred mainly in the first half), a noticeable deterioration in credit quality in Australia (even if from a low base) and is having to top up its provisions to cover credit market contingencies. The bank's impairment expense rose 29 per cent to $482 million.Another factor that could cause problems next year is that higher funding costs are likely to be maintained, pushing the bank's interest margin lower.Westpac reported net profit of $3.45 billion for the year to September, up 12 per cent on 2006. After adjusting for earnings on Westpac shares held by Westpac, hedging and significant items the bank reported cash earnings of $3.5 billion, up 13 per cent on the previous year.Earnings per share were up 13 per cent and the dividend payment was up by the same amount. The bank's return on equity was 24 per cent.Morgan said investors could expect to see the bank continue to produce such impressive numbers in future.The bank is budgeting for continued growth in wealth management. Earlier this week it launched a new superannuation product, Super for Life, that is linked to its online banking system, has a simple low-cost fee structure and has improved portability features.The wealth management division has also experienced a strong pick-up in insurance sales, which it expects to maintain, after making product changes that have facilitated higher cross-sell rates through the branches. Life insurance sales were up 58 per cent in 2007. Westpac's net interest margin declined by 10 basis points over the course of the year, from 2.29 to 2.19 per cent. This is within the five to 10