Casey's has spent 38 years selling convenience-store goods mainly in small midwestern towns with populations of 5, 000 or fewer.

FORBES: Inconvenience

IAWS, which specializes in bakery goods and convenience foods, has made a string of smart acquisitions across Europe and North America.

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For goods they might pick up as a convenience while in the store, like toothpaste or deodorant, pricing can be less sensitive.

ECONOMIST: How supermarkets have become department stores

"Non-traditional channels have become more important, especially as traffic in supermarkerts and traditional convenience stores have declined, " says Kenneth Harris, a packaged-goods consultant with Cannondale Associates in Evanston, Ill.

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So far, no large Indian supermarket chain has managed to replicate the convenience-store format successfully, because it's tough to offer goods on credit, personalize the service and stay profitable.

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