Commercial U.S. property/casualty insurance rates dropped an average of 4% in August compared with the same period last year, MarketScout said.

General liability experienced the largest rate decrease at 6%, the Dallas-based electronic insurance exchange said Tuesday. Crime, fiduciary and professional liability coverages registered the smallest decrease at 1%.

“Beginning in August of 2009, the composite P/C rate has been drifting between minus 5% and minus 3%, a very narrow range as compared to the wide swings during the last several years,” MarketScout CEO Richard Kerr said in a statement announcing the August results.

“August rates are down more than they were in July; however, the volume of business placed in August is considerably smaller than in most other months. No doubt, rate reductions continue, but over the last year, the degree of reductions has definitely moderated,” Mr. Kerr said.