The proposed initial public offering of the lenders' mortgage insurance business operated by Genworth in Australia could emphasise one little-known feature company: it is the fourth most profitable insurance firm in the country measured by underwriting profit.This puts the underwriting profit of the group ahead of much larger firms operating in general insurance such as Allianz and Suncorp.On the other hand, the underwriting profit of Genworth is only half that of QBE lenders' mortgage insurance, while the latter has only two-thirds the assets of the former.Mortgage insurance, while very much an insurance enterprise, is fundamental to the business of banking in Australia, since the underwriting policies of mortgage insurers in practice dictate the lending standards of most banks, building societies and credit unions. The industry depends on this insurance to offset the risks of making home loans to customers with small deposits.Half-yearly data published by the Australian Prudential Regulation Authority yesterday shows that Genworth Financial Mortgage Insurance Pty Ltd reported an underwriting profit of A$161 million in the year to June 2011.APRA put the net profit of Genworth of $191 million, its gross premium income for the year at $452 million, its total assets at $3.0 billion and its net assets at $1.8 billion.On this June 2011 snapshot of the insurance sector, Genworth accounts for 42 per cent of the premium income earned by mortgage insurance companies of $1.1 billion, 26 per cent of industry underwriting profit of $620 million and 31 per cent of industry net profit of $610 million.Last month, Genworth Financial said it plans to sell up to 40 per cent of its lenders' mortgage business in Australia, through a listing on the ASX.No date has been set for this listing, though it is likely to be some time in the first half of 2012.