Shareholders in denim duds retailer Guess? (NYSE:GES) endured a honey of a humdinger this morning when the stock opened down a good 3% on heavy volume. While I'm not normally one to sweat the market's short-term psychosis, as a shareholder myself, I was curious about the cause of this dip.

We got the answer a bit later, when the news broke that a research firm, Pacific Growth Equities, had downgraded Guess? from "overweight" to "equal weight." Again, this isn't the kind of thing we're normally too concerned with here at the Fool. We disagree with the Street's take on companies all the time, and there are a few firms, including Wachovia and Brean Murray, that share my opinion that prospects for Guess? are good. (Please don't hold that against me, or them.)

So why am I writing about this at all? Only to point out how absolutely silly the entire notion of upgrades and downgrades can be. Let's get back to the downgrader here: Pacific Growth Equities. Looking back, we see that the firm dubbed Guess? "overweight" when it initiated coverage in late October 2004. You may find it interesting that at the time, the stock was priced around $18 a share. By the end of December, it had cratered to below $12. If you bought on that October advice and sold on the panic, my condolences -- you were down 30%.

Now, I don't want to sound too critical here. We've all had our share of 30% losers that turn around and come back to reward us. But if Guess? was a good deal at $18 and it dropped to $12 without a material deficiency in the business, shouldn't it be an even better buy? Maybe not on Wall Street, where the herd would rather follow trends than swim against the cattle.

But truth be told, a few other Wall Street firms did think so. So did I. And over the past few months, it looks like Guess? has done a good job upping its profitability. As I've noted elsewhere, it seems on track for a steady, if modest, improvement. That's what makes today's notice so odd. Loved it at $18, hate it at $16? This is the kind of investment advice Wise People pay for?

True, there are concerns that slackening consumer demand and a glut of retail denim at places such as Abercrombie & Fitch (NYSE:ANF), Aeropostale (NYSE:ARO), American Eagle Outfitters (NASDAQ:AEOS), and Pacific Sun (NASDAQ:PSUN) might come back to bite them all in their jeans-clad derrieres, but that's hardly a new worry.

The moral of this tale is clear: Check out the numbers yourself, Fool. Invest in the quality you perceive, and tune out the background noise. Your timing may be off, but you need only look at the
Wise's mixed record to realize that their guesses are no better than yours.

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Seth Jayson is wondering whether he can get kids to pay $120 for his torn-up, worn-out 501s. At the time of publication, he had shares of Guess? and Aeropostale but no position in any other firm mentioned. View his stock holdings and Fool profile here. Fool rules are here.