Strong growth in Australian house prices over the past year has led to a halving of claims payouts by mortgage insurer Genworth Mortgage Insurance Australia, which is on track to exceed prospectus forecasts for its December financial year.Yesterday, Genworth reported a net profit of A$151.4 million for the six months to June - an increase of 130 per cent over the previous corresponding period. Underlying net profit, which strips out volatile investment returns, was $133.1 million - an increase of 40.7 per cent.When the company issued a prospectus for its initial public offering earlier this year it forecast a net profit of $231.1 million for the full year. Yesterday that forecast was revised, with the new target in a range between $231.1 million and $250 million. Genworth was listed on the Australian Securities Exchange in May, when the company's US parent, Genworth Financial, sold 34 per cent of its shares in the IPO, raising $583 million.The key to the good result is claims. The number of claims paid during the half-year was 881 - down from 1271 in the previous corresponding period. The payout was $55.4 million, compared with $102.8 million in the previous corresponding period.The average payout per claim was $62,900 - down from $80,900 in the June half last year.Genworth chief financial officer Georgette Nicholas said higher property values meant that Genworth could clear out many of its "aged delinquencies" (loans in arrears by more than 90 days) through property sales. It also meant that mortgagees selling properties were recovering more of their loans and, as a result, making smaller claims.Gross written premium of $313.6 million was up 14.9 per cent on the previous corresponding period and net earned premium was up 13.7 per cent.Genworth performed well on its key measures. The loss ratio, which calculates net claims as a proportion of net earned premium, was 19.6 per cent, compared with 32.1 per cent for the year to the end of December.The expense ratio, which expresses acquisition costs and underwriting expenses as a percentage of net earned premium, fell from 27.6 per cent in the June half last year to 27.3 per cent in the December half and to 26.6 per cent in the latest half. The company is ahead of its prospects forecast for an expense ratio of 27.6 per cent in the 2014 year.The combined ratio, which calculates claims plus underwriting expenses as a percentage of premium income (a combined ratio of over 100 per cent indicates an underwriting loss), fell from 69.9 per cent in the June half last year to 49.89 per cent in the December half and 46.2 per cent in the latest half. The company is well ahead of its prospect forecast for a combined ratio of 57.8 per cent in the 2014 year.The insurance margin, which expresses profit from underwriting and interest income on funds as a percentage of net earned premium, has increased from 35.8 per cent in the June half last year to 58.1 per cent in the December