Michigan’s economy benefited from a surge throughout the auto industry in September, according to a monthly economic report from Comerica Bank.

The bank’s Michigan Economic Activity Index ticked up one point to a level of 88. U.S. auto sales increased to 13.6 million units in November year to date, emboldening hopes of continued improvement. But Comerica’s chief economist, Robert Dye, cautioned against taking too optimistic a position.

“The climb out of the depths of the recession still looks very uneven, though, as hard hit areas within Michigan are stuck with very high unemployment rates,” he said.

Michigan’s unemployment rate fell to 10.6 percent in October, the first time it’s fallen under 11 percent since June. But Dye said the fall has as much to do with job growth as it does a decline in the labor force.

“Housing markets in Michigan and elsewhere are still a drag to economic growth and will likely be soft through 2012,” he said.

The Michigan Economic Activity Index weighs nine indicators that reflect construction, manufacturing and service activity, as well as job growth and consumer spending.