Rate rises gave US property and casualty (P&C) insurers a collective 4.4% increase in gross written premium last year, according to a new report from reinsurance broker Guy Carpenter.

Workers’ compensation written premium gained 8.2%, commercial auto liability was up 7.7% and product liability increased 6.9%, it says.

“Relatively low natural peril activity, impressive returns on the stock market, benefits from deferred tax assets and changes to pension accounting were among the many factors that contributed to a great result in [the year],” CEO US Operations Andrew Marcell says in the annual Insurance Risk Benchmarks report.

Large multiregional companies outperformed regional players, with regional diversification and risk management proving crucial to stable profitability, the report says.

The report suggests natural catastrophe risk and reserve risk pose the largest capital adequacy threats for excess and surplus carriers.

Despite concerns at the global economic situation and soft market conditions in many lines of business around the world, last year was positive for many US P&C insurers.

The report says the industry managed to continue its recent trend of reserve releases.