David Wolman urges small start-ups to tap into the third world market:

The Tata Group, India’s version of Acme and maker of the supercheap Nano automobile, recently introduced a $22 water purifier that works without electricity or running water. (Every few months it needs a new $6 filter.) A big-hearted, philanthropic, and important effort? You betcue the somber stats about preventable waterborne diseases. But check out the size of the market for a product like that: Some 900 million people worldwide lack access to clean water, 200 million of them in India alone. Tata is saving lives and making a killing.

Why aren't more American companies doing the same?

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