Clusters are highly-evolved regional economic ecosystems that are productive, competitive, and that innovate rapidly – they are constantly churning out new products and services.
	Clusters are complex systems with many feedback loops.  No one knows exactly how they come about.   Anchor companies appear to be important early on in some industries, spawning new life in the ecosystem:  Hewlett-Packard in Silicon Valley, Nokia in Helsinki, Medtronic in Minnesota.
	The term “cluster” was first used by Michael Porter’s in his landmark study The Competitive Advantage of Nations (1990).  Porter builds on the work of Albert Hirschman (1950s) on industrial linkages and Alfred Marshall (early 20th century) on the role of knowledge in industrial districts in the UK.
	Minnesota’s medical device industry is one of Porter’s preferred models for showing how clusters keep upgraded.