Underwriter Amlin said the trading environment has proved more challenging in the first four months of 2010 than in the previous year, with average rates falling 1.4%.Estimates of overall catastrophe losses in the period to 31 March 2010 reached $16bn, the worst first quarter on record.Gross written premium (before deduction of brokerage) was up 32.1% in the four months ended 30 April to £964m."Overall pricing remains steady but there remains considerable variance by class," the group said in a short statement."Loss activity has also risen with a number of notable catastrophe events, particularly the Chilean Earthquake in February and significant large losses, including the Deepwater Horizon rig explosion in April."