HSBC Bank Australia contributed US$373 million of pre-tax profit to HSBC plc earnings in 2015. The result was down on the previous year, when the local company earned $432 million.Since 2013, when it made a pre-tax profit of US$446 million, the earnings of the Australian bank have fallen 16.4 per cent.Earnings from commercial banking have fallen by almost half over that time. The retail banking and wealth management division has also had a sharp fall, while global banking and markets has grown.The residential mortgage book grew by two per cent from US$9.1 billion in 2014 to US$9.3 billion last year. Some exchange rate impact has to be taken into account because, according to Australian Prudential Regulation Authority figures, HSBC Bank Australia's mortgage book grew by 8.3 per cent over the 12 months to December. The bank does not provide any local commentary on its results.The value of the local bank's total loan book fell from $18.4 billion to $18.1 billion.