If you have spent any time reading about stock market basics, you have likely heard this golden rule: buy stocks with low Price-to-Earnings (PE) ratios because they are cheap, and avoid stocks with high PE ratios because they are expensive. For steady businesses like consumer goods or IT, this rule works reasonably well. But if you apply this same logic to commodity businesses like steel, cement, sugar, or paper, you will likely lose money.

The Nature of Cyclical Stocks

Commodity companies do not control the price of what they sell. A steel manufacturer cannot decide to sell steel at a premium just because they have a great brand. They must sell at the prevailing global market price. When global supply is tight, commodity prices skyrocket. The company's profits explode, even if management did nothing new. But when global supply increases, those same commodity prices crash, and profits vanish.

This extreme swing in profits creates a counter-intuitive phenomenon. Because the PE ratio is calculated using past earnings, the ratio behaves in a completely inverted way for cyclical stocks. To understand this, let us look at the standard formula.

A Worked Example: Metal India

Let us walk through a step-by-step example using a fictional cyclical business called Metal India. We will trace its stock price, earnings per share (EPS), and PE ratio over a typical six-year commodity cycle.

Why the Peak Looks Cheap and the Bottom Looks Expensive

Look closely at Year 4 and Year 5 in our charts. A PE ratio of 5x looks incredibly cheap. A beginner investor looking at a stock screener would see a highly profitable company trading at a single-digit PE and think it is an absolute bargain. But in reality, this is the most dangerous time to buy. The earnings are at their cyclical peak and are completely unsustainable. Once global commodity prices drop, the earnings denominator collapses, and the stock price follows.

Conversely, look at Year 1. A PE ratio of 50x looks outrageously expensive. Most conservative investors would run away. Yet, this is actually the safest time to buy. The earnings are at rock bottom, and any recovery in the commodity cycle will send profits—and the stock price—soaring, which will eventually make the PE ratio look 'cheap' again.

You can easily spot these cyclical patterns and track historical PE ranges by searching for any commodity stock on the stock-analyze.com valuation page.