Supercenters are the obvious winner, and a new study from The Nielsen Co. reports that in 2008, consumers increased their spending at supercenters in nearly every category--including dairy, dry grocery and prescription drugs--making it the only retail channel to have unit growth over the prior year, up 1% from 2007. "Mass merchandisers and grocery stores are feeling the impact of the supercenter," the company says in its analysis. "The grocery channel is not recession proof."

But in the current retail free-for-all, defining "winning" is more complicated. For example, Nielsen reports that four channels saw sales gains from new shoppers fleeing higher prices--supercenters, drug stores, club stores and dollar stores. Yet in addition to supercenters, gains were offset by an overall decline in unit sales, as consumers cut back spending.

Retailers are struggling to understand who these channel-changers are. For example, a bright spot for grocery stores has been prescriptions, as some consumers have turned away from higher-priced drug stores. And for drug stores, it has been health and beauty, as consumers trade down from department stores. There's even trading up in trading down, as shoppers in discount stores like TJMaxx have access to more higher-end brands than in the past.

But the constant downward drift can be perplexing--and TNS Retail Forward, a Columbus, Ohio-based sales consultancy, says it may even be hurting Walmart's results. Its ongoing ShopperScape reports that in December, "Walmart had a significantly smaller share of shoppers with incomes under $25,000, and a significantly larger share of shoppers with incomes more than $100,000." These income-related shifts were not as pronounced in January as they were in December, the company reports.

While conventional wisdom holds that a more affluent consumer is always better, Retail Forward says low-income shoppers make at least one more trek to Walmart monthly than higher-end consumers, with both groups spending roughly equal amounts per trip.

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