US commercial rates grew 3% last month compared with 2% in April, according to analyst MarketScout.

CEO Richard Kerr says the development was unexpected because “market sentiment supports rate moderation”.

“However, as we all know, trends bump along before establishing a true direction,” he said.

Commercial property, business owners’ policies and general liability were all up 3%.

Rate rises on accounts with premiums of $US25,000-$US250,000 ($26,888-$268,887) grew to 3%.

Rises on $US250,000 to $US1 million ($1.08 million) accounts increased to 2%.

Personal rates increased 3%.

Mr Kerr says smaller insurers vary pricing almost monthly, but large insurers dominate the personal lines market.

“Because of their size and ability to withstand market trends, the large insurers don’t normally respond to unfounded price aberrations in any given market. Thus… another month of steady results at plus 3%.”