Arch Capital Group Ltd posted net income of $316 million for the fourth quarter.The Bermudian re/insurer said the profit, up from $126 million in the corresponding period of 2018, broke down to 76 cents per share and represented a 12 per cent annualised return on average common equity.For the full year, net income more than doubled to $1.59 billion from $713.6 million in 2018.After-tax operating income for the fourth quarter was $308.4 million, or 74 cents per share, exceeding the 68 cents per share consensus estimate of analysts tracked by Yahoo Finance.Arch said pre-tax current accident year catastrophic losses, net of reinsurance and reinstatement premiums were $30.4 million.Favourable development in prior year loss reserves totalled $54.7 million.Arch’s combined ratio — a measure of underwriting profitability representing the proportion of premium dollars spent on claims and expenses — was 81.4 per cent.Book value per common share was $26.42 at the end of last year, a 3.2 per cent increase for the fourth quarter and a 22.8 per cent increase for the year.