DALLAS—The average rate for property/casualty insurance fell 6% in May compared with an 11% decline a year ago, MarketScout said Friday.

The Dallas-based electronic insurance exchange said the average rate for workers compensation insurance dropped 7% year-over-year, while lines such as commercial property and general liability insurance declined 5% and 6%, respectively.

Service accounts saw an average 8% decline in May vs. a year earlier, while manufacturing saw a 7% average decline.

“Every sensible economic indicator tells us rates should be increasing, yet there are still three large admitted, publicly traded insurers clamoring for premium, seemingly at any rate and continuing to prolong the soft market,” Richard Kerr, chief executive officer of MarketScout, said in a statement.

He did not name the insurers, which he said are contributing to the market's decline with “irresponsible” underwriting. He projected the market would turn by year-end as a majority of insurers are “making appropriate underwriting decisions.”