Investment research firm Morningstar said it sees the Marceilus Shale in the US Northeast as the primary driver of natural gas production growth in the coming years. Morningstar energy strategist Mark Hanson noted in a recent report that the Pennsylvania-centered play accounted for just 2% of domestic gas output in 2007, but at year-end 2013 it was producing close to 20% of the nation's gas.
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