Chasing the next Amazon and investing in grassroots startups are valuable economic development strategies. But Southeast Michigan could more significantly grow and diversify its economy by directing support to high-growth companies in the middle, according to a new report released this week.

Companies with 50 or more employees, launched by local entrepreneurs and operating in industries that draw income from outside the region, are creating the bulk of jobs locally and nationally in the country's most prosperous cities.

Yet over the past 15 years, Southeast Michigan has lagged other parts of the country in generating those high-growth businesses, according to "Southeast Michigan's Competitive Advantages in Entrepreneurship," a report set to be released Tuesday by the William Davidson Foundation and Endeavor Insight, the research arm of New York City-based Endeavor Global Inc.

When it comes to economic development, "regionally, we spend a lot of bandwidth focused on businesses at either bookend of the size continuum, small and large," said Darin McKeever, president and CEO of the Birmingham-based William Davidson Foundation.

A Thursday session hosted by the foundation at the Mackinac Policy Conference will include discussion of the report and its recommendations.

"Small neighborhood businesses and early stage startups are critically important, not only for job creation and the individual families they support, but they ultimately help define our regional identity," McKeever said.

Large companies are an important part of the ecosystem that can never be undervalued, he said.