Quick quiz: How many times has America had a negative savings rate for an entire year?

Quick answer: Three. (According to our friends at the Associated Press)

More interesting question: What years were those?

Interesting, but scary answer: 1932 and 1933 -- when the country was in the throes of the Great Depression -- and then way back in 2005.

Yes, according to information released today by the Commerce Department, Americans ratcheted up their spending by nearly 0.9% in December, on a personal income increase of only 0.4%. That sent the country's personal savings rate to a negative 0.7% for the month, and a negative 0.5% for the entire year.

What should investors take away from this? I honestly don't know. I don't pretend to be an economist. But here's what this investor sometimes thinks, in the deep, dark of the night when the branches become monster claws and the murder of crows gets vocal.

Cue spooky theremin music.

Sell all those retail stocks. Now. The real American cash machine isn't the ATM on the corner, but the roof over our heads. With everyone borrowing this cheap money and spending it on stuff, what happens when -- not if -- this screeches to a halt?

During the monster hour, I imagine this scenario: All that fake wealth will go poof. The ARMs will readjust. Panicked amateur home-flippers will unhook themselves from their money-losing "investments," and with the easy gains of faux equity gone, the money flow will dry up.

What'll happen to those giant same-store sales gains at Abercrombie & Fitch (NYSE:ANF)? Would a fragile Wet Seal slide down the hole, to be seen again nevermore? Could Ford (NYSE:F) and GM (NYSE:GM) survive an even bigger sales downturn than the one they've already engineered by their excessive discounting?

The more I see data like that savings rate -- or evidence of a continued cooling in the vaporous economic engine that is the housing-market -- the more I'm going to start moving money into companies that sell what people need, not what people can live without. So long, Best Buy (NYSE:BBY), hello Colgate-Palmolive (NYSE:CL). Urban Outfitters? It's been fun, but if it comes to a point where people have to choose between $180 jeans (slimming and edgy as they may be) or corn flakes for the kids, or gas for the drive to work, I'm betting on the likes of Wal-Mart (NYSE:WMT) and ExxonMobil (NYSE:XOM).

I'm not making these moves now, but I'm seriously pondering many of them. How long can we, as a nation and as individuals, borrow our way to affluence? How long before a readjustment to reality flops onto the top and bottom line at companies that depend on discretionary spending to survive? I'm pretty sure the answers to both these questions are the same: "Not forever."

Seth Jayson last predicted a falling sky last week. He figures, like a broken clock, he'll be right sooner or later. At the time of publication, he had no positions in any company mentioned here. View his stock holdings and Fool profile here . Best Buy is a Motley Fool Stock Advisor pick. Fool rules are here .