Wellington Underwriting said underwriting conditions remained favourable in 2004, with the 5% overall decrease in rates in line with expectations as business terms and conditions held.
The group said: "2004 rates are still well above those of 1993, which was an excellent underwriting year."
It said estimates for the impact of hurricanes Charley, Frances, Ivan and Jeanne remain unchanged and within expectations, while the Asian tsunami catastrophe is not expected to have a material impact on results.
Wellington said Syndicate 2020's open year underwriting profits have been protected against the recent weakening of the dollar thanks to its "proactive hedging policy".
It warned, however, that should the more recent rate of exchange of £1 for $1.91 continue, "Syndicate 2020's distribution of potential 2005 year account profits in 2008 would be impacted by that weakening".