CLAYTON — When many St. Louis County homeowners learned last week that their property assessments — a key factor in determining property taxes — had dropped, owners of commercial property got sobering news.

Commercial values, and taxes, are headed higher, according to the county. It reported a median rise of 8.3 percent in the values of the county's 13,500 commercial properties.

That change, between 2007 and this year, is almost the opposite of the 9 percent drop in median values of residential properties.

Business owners across the county were shocked, and many angered, to see big jumps in their values. They wondered how that could happen in a down economy — and in a year when the county's residential values dropped so much.