Walmart

No one else has Walmart's footprint. About 11,000 stores and clubs sit within ten miles of more than 90 percent of Americans, which lets orders ship from the building down the road instead of a warehouse across the country. That reach helped build a company now worth roughly 910 billion dollars, and it is extremely expensive for anyone else to copy.

Walmart sells what people need no matter what the economy is doing, and groceries make up roughly 60 percent of sales. That keeps shoppers coming back in good times and bad, and revenue is still climbing about 4.7 percent a year off an enormous base. Higher income households have been shopping there more too, not just bargain hunters.

The pace has clearly slowed. Revenue growth has eased to roughly 4.7 percent a year, well below the 7 percent stretch shoppers and owners got used to. The stock is still priced like a much faster grower, so a merely fine quarter can knock the price down hard.

Walmart keeps only about 3 dollars of profit for every 100 dollars in sales, so there is almost no cushion. When fuel, shipping, or labor costs rise, the company usually eats the difference rather than charging shoppers more. With margins that thin, small cost increases hit the bottom line fast.