QBE shares plunge nearly 20% Investors have punished insurance giant QBE's shares following a large earnings downgrade and the retirement of its chairman. QBE shares had plunged $2.98 or 19.3 per cent, to $12.47 by midday. The company, Australia's largest insurer by market, flagged a $250 million net loss for calendar 2013. QBE's underperforming North American business is hurting the overall company, leading to $600 million in goodwill writedowns to its value. QBE has been exposed to claims related to the worst draught in 50 years in the US, hurting crop prices and yields. An extensive investigation by internal and external actuaries had also led to a $300 million increase in accident claims provisions from the previous year. That related to workers compensation, general liability and construction defects risks. Other adverse effects out of the US have included damage from Superstorm Sandy, low interest rates and an operating loss from its lender placed business, which provides mortgage insurance. Chief executive John Neal on Monday said there was a clear need to restructure the North American business. It would still be a viable, profitable business next year, albeit on a much smaller scale, he said. "It is disappointing that in a year when we made excellent progress in improving our current accident year profitability, strengthened our key capital ratios and our balance sheet, successfully launched our operational transformation program and strengthened our executive team, that we continue to be hampered by the past," he said. The company also announced chairman Belinda Hutchinson would leave QBE in March, to be replaced by fellow director Marty Becker. It also said it expected its insurance profit margin to fall from eight per cent to six per cent and forecast a fall in cash profit to $850 million in 2013 from $1.04 billion.