Bloomberg Businessweek reports that Great Lakes cargo shipping saw a 14% increase during the last year, fueled in large part by an upturn in Michigan's economy. Increasing demand for iron ore and limestone are driving increases in the shipping business, and the return to profitability by Michigan's automakers is being read as a sign of good things to come. In the meantime, ports such as Detroit and Duluth have seen significant economic growth associated with the increased traffic.