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A stock versus the market

A stock can rise and still trail the market. Race a stock against the S&P 500 from the same start and call the winner — the gap between them is relative strength.

So far you’ve judged a stock on its own chart. Now judge it against the one benchmark that matters — the market.

A stock can be up 10% and still lose. If the S&P 500 gained 15% over the same span, the stock underperformed — you'd have done better just owning the index. That gap is what relative strength measures.

"Up" is not "ahead." A stock climbing steadily can trail a market that climbed faster — and a stock that fell can win, if the market fell harder. What matters isn't the stock's own move; it's the gap between it and the market.

Below, a stock (bright) and the S&P 500 (dim) both start at 100 and run the window. Watch who leads — then call the finish: did the stock beat the market or lag it? Reveal the gap and see.

The trap is the halftime lead. In two of those races the stock is ahead midway and loses at the tape — because relative strength is about where the gap ends, not where it led. And in the down race, the faller won: both dropped, it just dropped less.

The read is one question: is the stock outperforming the S&P 500 over the window? Not by how much, not for how long — just which side of the market it finished on. Short windows flip often as a few strong days swing the gap; longer ones steady out as small daily differences compound.