With a six month migration period ahead, developers and users may have hard choices to make.

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An earlier period of great migration came to an end, for example, when America some 90 years ago shut its doors to immigrants for a while.

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Migration data for the most recent one-year period available, July 2010 t0 July 2011, show the Great Recession has shaken the rankings up quite a bit within the circle of fast-growth regions.

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