Time was, “As General Motors goes, so goes the nation.” What would be the suitable substitute for GM in post-industrial, post-modern, post-Bretton Woods America? Wal-Mart? Or maybe Starbucks?

Starbucks, the coffee house chain, on Wednesday blamed a “sharp weakening” in the consumer economy for an unexpected decline in its US sales, sending its shares plunging more than 10 per cent in after-hours trading.

Howard Schultz, who returned to the role of chief executive in January, said “the current economic environment is the weakest in our company’s history”, citing the housing slump and rising energy and food costs.

The company’s history goes back to 1971, the year Bretton Woods fell apart and Nixon closed the gold window. So for Schultz, things are worse now than the double-dip recession in the early 80s, the worst of the postwar era. Grim stuff indeed for a company whose entire business model is built on an “affordable luxury.”On the subject of historical comparisons, Robert Shiller — he of the Case/Shiller home price index — is going all the way back to the Great Depression, when housing prices dropped 30%. He says an even bigger drop is possible now (with prices having already fallen 15% in his estimation).

Home prices rose about 85% from 1997 to 2006 adjusted for inflation, the biggest national housing boom in U.S. history, Mr. Shiller said. “Basically we’re in uncharted territory,” he said. “It seems we have developed a speculative culture about housing that never existed on a national basis before.” Many people became convinced that housing prices would increase 10% annually, a notion Mr. Shiller called crazy.

And there’s another property time-bomb looming. In fact, it’s one of five “super shocks” about to hit the U.S. economy and stock market in the very near future. For a seven-part defense strategy, check out this special report.