Bullish Percent Index: Counting P&F Buy Signals

Key Takeaways

• BPI equals the count of stocks on a current P&F buy signal divided by total stocks, expressed as a percentage.
• Values above 70 are considered overbought and values below 30 oversold, with the 50 line dividing bull and bear bias.
• Most investors misuse BPI by trading every cross of 50 instead of waiting for the index to reverse from an extreme.
• BPI is published for sectors and major indices, letting you compare internal participation across slices of the market.

What It Is

BPI is calculated daily for a defined group of stocks. The most widely watched version covers the S&P 500, with parallel BPI series published for the Dow, Nasdaq 100, and each of the eleven S&P sectors. The input is purely point and figure, which means each stock is in one of two states: on a buy signal after a double-top breakout, or on a sell signal after a double-bottom breakdown.

A stock holds its current signal until the opposite signal triggers. This binary state machine is what makes BPI different from indicators that ride continuous price values; the underlying inputs only flip on confirmed breakouts.

The Intuition

Imagine 500 light switches, one per stock. A switch is on when the stock has flipped to a P&F buy signal and off when it has flipped to a sell signal. BPI is simply the share of switches that are on.

When that share rises, more stocks are joining the offensive side of the market. When it falls, more are switching to defense. Because flipping a switch requires a confirmed P&F reversal, BPI ignores the noise of single-day rallies and selloffs and only changes when a stock genuinely changes character.

How It Works

The formula is:

BPI = 100 * (Number of stocks on P&F buy signal) / (Total stocks in universe)

The reading sits in [0, 100]. Traditional thresholds, used since Cohen's original work and codified by Earl Blumenthal and Mike Burke in the 1970s, are:

• Above 70: overbought; offense holds the ball but risk of reversal is rising
• 50 to 70: bullish bias with room to run
• 30 to 50: bearish bias
• Below 30: oversold; defense holds the ball

Practitioners look for two kinds of confirmed events. A "bull alert" is a reversal up from below 30 by at least 6 percentage points. A "bear alert" is a reversal down from above 70 by at least 6 percentage points. Mid-range fluctuations are less reliable.

Worked Example

Suppose on a given Friday the S&P 500 BPI prints at 78. The reading is overbought. Traders raise stops but do not short the index simply because the level is high; markets can stay overbought for months during strong uptrends.

Two weeks later the index prints 71 after a sequence of P&F sell-signal triggers. That is a confirmed reversal from above 70 of more than 6 points. Historically this kind of cross has flagged near-term tops in cyclical advances. A defensive posture is justified, with the threshold for re-entry being a return above 70 or a fresh bull alert from below 30 after the correction.

If BPI later falls to 28 and then turns and crosses back above 30, the bull alert reverses the prior bear bias. That sequence often coincides with capitulation lows.

Common Mistakes

1. Trading every 50-line cross. The signal-to-noise ratio at 50 is poor. Use 70 and 30 alerts as primary triggers.
2. Treating sector BPIs like the index BPI. Sector indices have fewer constituents, so single-stock breakouts move the reading more. Use sector BPI for relative-rotation work, not for swing timing.
3. Ignoring the box size. P&F buy signals depend on box size and reversal amount. Different vendors use different defaults; BPI from one source may not match another.
4. Confusing BPI with the percent above moving average. Both measure breadth, but BPI changes only on P&F state flips while moving-average breadth changes daily with price.
5. Forgetting the lag. A P&F buy signal requires multiple boxes in a column, so BPI lags small reversals by several days. That smoothing is a feature, not a bug, but it does slow the indicator.

Frequently Asked Questions

What is bullish percent index BPI in simple terms? BPI is the percentage of stocks in an index that currently show a point-and-figure buy signal. A reading of 70 means 70 percent of the names are on a buy and the broader index has wide participation.

How does bullish percent index BPI affect investment decisions? Investors use BPI to gauge whether a rally has broad participation and to time bias shifts. Confirmed reversals from above 70 or below 30 historically align with intermediate-term turning points in equity indices.

What is a real-world example of BPI? Near the March 2020 lows the S&P 500 BPI fell into the single digits, an extreme oversold print. The subsequent reversal back above 30 was an unusually clean bull alert that preceded a strong multi-month advance.

How can investors use BPI effectively? Watch the 70 and 30 lines for confirmed reversals of at least 6 points, ignore mid-range chop, and use sector BPIs to spot internal rotations before they show up in headline-index price.

How is BPI different from the advance-decline line? The AD line tracks net advancing issues every day and changes constantly. BPI changes only when individual stocks confirm a P&F state flip, making it slower but less prone to single-day noise.

Sources

1. StockCharts ChartSchool. Bullish Percent Index (BPI). https://chartschool.stockcharts.com/table-of-contents/market-indicators/bullish-percent-index-bpi
2. StockCharts ChartSchool. StockCharts Bullish Percent Index. https://chartschool.stockcharts.com/table-of-contents/index-and-market-indicator-catalog/stockcharts-bullish-percent-index
3. StockCharts Insider. Bullish Percent Index: A P&F Approach to Measuring Market Strength. https://articles.stockcharts.com/article/stockcharts-insider-bullish-percent-index-a-p-f-approach-to-measuring-market-strength/
4. AAII. Bullish Percent Index. https://www.aaii.com/journal/article/bullish-percent-index

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.