However good your stock is, most leaders pull back together when the broad market breaks. Statistically, a large share of any single stock’s movement is driven by the overall market’s direction. So seasoned traders ask, before picking a stock, "is this an environment worth buying in?" The core tool for that top-down judgment is market breadth.
The index alone isn’t enough
Indexes like the S&P 500 or KOSPI are dominated by a few mega-caps. A handful of large stocks can lift the index while most others fall — an illusion of strength. That’s how you get an index at new highs with nothing worth buying underneath. The market’s true health shows in what hides behind the index: how many stocks are rising together.
Gauges of breadth
- Advancing-stock ratio: the share of stocks rising (or trending strongly). The higher it is, the more broad-based and healthy the advance.
- New highs vs. new lows: 52-week new highs minus new lows. Positive and rising is strong; turning negative is a warning.
- Number of passing stocks: how many names clear the eight conditions each day in Trend Screener. A rising count means more leaders; a sharp drop means the broad trend is weakening.
Scale aggression to the regime
Combine breadth with the index trend and you can roughly read the regime.
- Attack: index rising above its 200-day, advancing ratio and passing counts climbing. Press leader breakouts.
- Neutral / caution: the index holds but breadth deteriorates (only mega-caps rise). Cut new buys and tighten stops.
- Defense: index below the 200-day, new lows expanding. Most breakouts fail — raise cash and wait.
Trend Screener’s market-environment page
Trend Screener’s market environment page charts several KPIs daily — passing-stock counts, average relative strength, breadth, new-high trends. Checking their direction before picking individual names helps you judge whether it’s time to press breakouts or to reduce risk and wait. Trend following performs best when strong selection meets the right market timing.