Re/insurance companies may be over-reliant on computer models which tend to be very similar to each other across the industry.That is the view of Marc Grandisson, CEO of Arch Worldwide Reinsurance Group, who was speaking at the PwC/S&P Bermuda (Re)insurance 2011 conference last week.“The beauty of underwriting is that no-one really knows what’s going to happen,” Mr Grandission, himself an actuary, told delegates. “You have to pick and choose where you’re going. It’s very much a judgment call. Those who win can win pretty big.“We have so many actuaries going to the fifth decimal place, when sometimes we miss what is happening on the left hand side of the decimal point.”The use of standardised models across the industry was effectively correlating risks within the industry, Mr Grandisson said.“Models are relied upon much more than they were 10 or 15 years ago,” he said. “Everybody is using the same model and so when something unexpected happens, then everyone makes big losses.”Models were useful for benchmarking and for selecting risks, he added, but not at giving an absolute view, Mr Grandisson added.