Retailers are investing heavily to track consumers' behaviour in an attempt to work out what they might want to buy and how much they are willing to pay.

ECONOMIST: America's shoppers

One factor behind disappointed expectations of America's performance could be the behaviour of consumers.

ECONOMIST: Still on amber

Driving the strategy of all these firms is the shifting behaviour of consumers. eBay's business, in particular, has been moulded by its users.

ECONOMIST: eBay