The simple story
Here at the Fool, we've long cautioned investors to keep a close eye on inventory levels. We think a quarterly checkup is key to spotting potential problems, especially with seasonally dependent, fashion-oriented retailers like Coach (NYSE:COH) or Gap (NYSE:GPS) and tech companies that operate in the fast lane, like Intel (NASDAQ:INTC) or Cisco (NASDAQ:CSCO). Remember that service businesses or companies that sell the same thing all the time, like Coca-Cola (NYSE:KO) or Cemex (NYSE:CX), may not be as inventory-sensitive as other manufacturers and retailers. The former type share a big potential problem: Goods that sit on the shelf for a few extra months are as good as garbage. This can be especially troublesome for small-cap companies -- the type we specialize in at Motley FoolHidden Gems.

That's because too often, the only way to get rid of stale merchandise is to put it on sale, hurting profitability. In extreme cases, companies may even need to write off those purses and chips entirely, which involves taking a near complete hit on the goods and -- rumor has it -- sending them out to be ground up into meat sauce for crooked school lunch programs.

Basic guidelines
To keep a handle on inventories, we often use a simple rule of thumb: Measured across comparable quarters (year-over-year), inventory increases ought to roughly parallel revenue increases. Simply put, if inventories grow 35%, we hope that sales will have grown that much as well. Of course, if a company can reduce its inventory growth relative to its sales growth, that might be preferable by freeing up money that's essentially sitting around fallow on the shelves. Hey, even bank interest is better than no return at all.

Conversely, if inventory bloats at a rate beyond the growth in sales, we expect a darn good explanation.

Exception to the rule
Fools should be aware that there's one type of inventory bulge we actually like to see. In fact, it can be a key to identifying a potential Hidden Gem before the Street shows up with its shovels and tries jumping our claim. This is something we call "positive inventory divergence," which is a concept taken from one of our favorite books, Thornton O'glove's Quality of Earnings.

There are different kinds of inventory: raw materials, works in process, and finished goods. To take a hypothetical example, if we make ovens, like Hidden Gems' 250-plus-percent returning superstock Middleby (NASDAQ:MIDD), we will have an inventory of stuff like steel and bolts (raw), ovens with no doors attached (works in process), and maybe even ovens (finished goods). You won't usually find inventory broken down with this kind of detail in earnings releases, but it should appear in the 10-Qs that you can get from the SEC.

Here's the kind of bloating inventory that can be a clue to future glory. If Middleby is ramping up for increased demand it sees -- but may not have reported to the Street -- it may very well be growing certain parts of its inventory at a rate faster than sales. We would expect to see these healthy bulges in the area of raw materials and works in process. To go one further, if this is a company that is subject to continuing increases in commodity prices, we might also cheer its decision to buy extra raw materials while the prices are still lower than what it expects to have to shell out in the future.

If, on the other hand, the bloat comes in finished goods, this might be a sign that expected sales haven't materialized, and management has some 'splaining to do.

Here's Middleby's inventory story as of the April quarter, 2005 and 2004.

2005

2004

% Difference

Revenues

$74,889

$62,463

+20%

Raw Materials

$7,942

$5,120

+55%

Works in Process

$5,456

$4,619

+18%

Finished Goods

$23,801

$18,686

+27%

Total Inventory*

$37,186

$28,904

+29%

* Net of LIFO adjustments.

As the case of Middleby shows (as of the April quarter of this year), what looks at first like an oversized inventory spike is actually a bit more complex. Although total inventory growth outran revenue growth by a difference of 9 points, a very healthy chunk of the increase came in raw materials. Finished goods also piled up a bit more quickly than revenues did, which should have the folks at the dedicated Hidden Gems board mulling over the reasons.

Foolish bottom line
When you're scanning your quarterly earnings reports, remember that many of the numbers mask situations that are more complex than they appear. When in doubt, listen to the conference call, give investor relations a jingle yourself, and make sure to check back when the quarterly report is filed. What at first looks like a problem may indeed be a sign of good things to come.

Related Foolishness:

Looking for the latest inventory divergents and other small caps operating under the radar? A free trial of Motley Fool Hidden Gems lets you join the hunt.

Coca-Cola is a Motley Fool Inside Value pick. Gap is a Motley Fool Stock Advisor pick.

Seth Jayson loves digging past the obvious, even though it makes his brain hurt. At the time of publication, he had positions in no company mentioned. View his stock holdings and Fool profile here. Fool rules are here.