US property and casualty and professional liability rates increased 5% on average last month, according to insurance exchange MarketScout.

The highest rises were in commercial property and workers’ compensation, up 6%.

Commercial auto and umbrella/excess grew 5%, while general liability was up 4%.

Business interruption, inland marine, professional liability and directors’ and officers’ liability increased 3%, while surety rose 2%.

“The market is bumping along in a continued slow-but-steady path towards overall increases,” MarketScout CEO Richard Kerr said.

“For the rest of [the year] we expect some months with lower composite increases than prior months, but the general direction… will be upward, unless new capacity enters the market.”

Some industry analysts think Berkshire Hathaway might launch a new underwriter, Mr Kerr says. “It could have an impact on pricing.”

Rates on medium accounts – $US25,001 to $US250,000 ($24,824 to $248,232) – increased 6% in April.

“Jumbo” accounts, of more than $US1 million ($992,796), saw rate rises fall to 3% from 5% in March.

Small accounts of up to $US25,000 and large accounts of $US250,001 to $US1 million rose 5%.

By industry class, manufacturing increased 7%, transportation and contracting grew 5% and energy was up 4%.

Personal lines rates also increased, MarketScout says.

The US composite rate index was up 3% last month, compared with the March rise of 4%.

“April traditionally is a good month for personal lines insurers, because the spring storms have not yet hit – thereby avoiding tornado and hail claims – and flooding usually occurs a bit later in the year,” Mr Kerr said.

“Perhaps the psychology of lower filed claims and the time passing since Superstorm Sandy had some impact on insurers’ pricing.”

Homeowners’ rates for properties worth more than $US1 million grew 4%, while homes below that threshold increased 3%.

Personal auto cover was up 3% and rates for personal articles including wine collections, art and jewellery rose 3%.