How can America's corporations so defy gravity? Ever adaptive, they have evolved a business model that enables them to make money even while the strapped American consumer has cut back on purchasing. For one thing, they are increasingly selling and producing overseas. General Motors is going like gangbusters in China, where it now sells more cars than it does in the United States. In China, GM employs 32,000 assembly-line workers; that's just 20,000 fewer than the number of such workers it has in the States. And those American workers aren't making what they used to; new hires get $14 an hour, roughly half of what veterans pull down.