Coppock Curve: A Long-Term Buy Signal Indicator

Key Takeaways

• Coppock curve indicator is a 10-month weighted moving average of the sum of a 14-month and 11-month rate of change.
• Cross from below zero to above zero is read as a long-term buy signal for the index it is applied to.
• The indicator is built for monthly charts and major bottoms, not for swing trading or intraday timing.
• It is a one-sided tool by design; Coppock did not propose a sell rule, and most practitioners use other indicators for exits.

What It Is

The Coppock curve indicator is a single oscillator line that crosses around zero. It is applied to monthly bars of a broad index, most often the S&P 500 or a national equity benchmark, and it updates once per month at the close.

A bullish crossing through zero from below is the only signal in the original design. Coppock proposed it as a "buy" trigger for long-term equity allocations after deep declines. The curve is not symmetrical and does not generate sell signals in the same way.

The Intuition

Coppock was asked by Episcopal church investors how to time equity exposure after market crashes. He spoke to a priest who told him that grief from a major loss typically lasted between 11 and 14 months. Coppock used that as the look-back window for his rate-of-change inputs, on the analogy that markets need a similar period to recover from a major downdraft.

The two rate-of-change lines capture how far price is above or below its level around that healing window. The 10-month weighted average smooths the combined signal so that only durable improvements push the line above zero. The structure filters out small rallies inside bear markets.

How It Works

The classic formula on monthly closes is:

ROC14 = 100 * (Close - Close_14_months_ago) / Close_14_months_ago
ROC11 = 100 * (Close - Close_11_months_ago) / Close_11_months_ago

Coppock = WMA10( ROC14 + ROC11 )

WMA10 is a 10-period linearly weighted moving average. The most recent month carries weight 10, the previous month weight 9, and so on down to 1 for the oldest month inside the window.

The signal rules are simple:

• A cross from negative to positive territory is a long-term buy.
• A cross from positive to negative territory is generally ignored, although some practitioners use it as a warning to lighten exposure.
• Larger negative readings preceding the cross indicate a deeper prior bear market, which historically has been associated with stronger subsequent rallies.

Coppock published the indicator with monthly inputs, but modern charting packages allow daily, weekly, or any other interval. Faster intervals turn the curve into a different tool that produces many more crossings and many more false signals.

Worked Example

Suppose the S&P 500 monthly closes look like the following after a long decline:

Now           : 3,200
14 months ago : 4,000
11 months ago : 3,500

Compute the two rate-of-change values:

ROC14 = 100 * (3,200 - 4,000) / 4,000 = -20.0%
ROC11 = 100 * (3,200 - 3,500) / 3,500 = -8.6%
Sum   = -28.6%

Now imagine the 10-month weighted moving average of the rolling sum had been deeply negative, say around -40, and has been rising for several months as the market recovered. This month's sum of -28.6 is less negative than the historical inputs in the window, so the WMA10 ticks up further.

When the WMA10 finally crosses from below zero to above zero, that is the Coppock buy signal. Historically, that has occurred a few months after major equity bottoms such as 1982, 2003, and 2009, though the indicator is not always perfectly timed and has produced occasional whipsaws.

Common Mistakes

1. Using it for short-term trading. The Coppock curve is built around 11, 14, and 10 months. Trying to use the same parameters on daily bars produces a different indicator with very different statistical properties.

2. Treating it as a complete system. The classic Coppock has only a buy rule. Without a separate exit framework, equity is held indefinitely after the signal. Most practitioners pair it with a trend filter or a regime indicator for exits.

3. Reading every zero cross as a major bottom. Some Coppock turns happen inside ongoing bear markets and reverse a few months later. Confirm the signal with at least one other indicator such as the 200-day SMA on the index.

4. Applying it to single stocks. The indicator was designed for broad indices where breadth and diversification smooth the underlying. Applied to single names, signals fire often and reliability drops.

5. Tweaking the periods without testing. The 11, 14, and 10 numbers have been studied for decades. Shortening them produces a faster but noisier oscillator. Backtest any change before relying on it.

Frequently Asked Questions

What is the Coppock curve in simple terms? The Coppock curve is a slow momentum indicator on monthly data that generates one signal at a time. When it crosses above zero from below, it suggests a major market bottom has formed.

How does the Coppock curve affect investment decisions? Long-term investors use the upward zero cross as a green light to increase equity exposure after a bear market. It is rarely used for short-term trading because the smoothing is too slow.

What is a real-world example of the Coppock curve? On the S&P 500 monthly chart, the Coppock curve crossed above zero in 1982, 1991, 2003, and 2009, each near the start of an extended bull market. It has also produced a few smaller whipsaws between those turns.

How can investors use the Coppock curve effectively? Apply it to a broad index on monthly bars, confirm with a 200-day or 12-month SMA filter, and use it to time large allocation changes rather than individual trade entries.

How is the Coppock curve different from MACD? MACD uses two exponential averages on much shorter windows and fires many signals per year. Coppock uses two rate-of-change values over roughly a year and is designed to fire only at major turning points.

Sources

1. StockCharts ChartSchool. "Coppock Curve." https://chartschool.stockcharts.com/table-of-contents/technical-indicators-and-overlays/technical-indicators/coppock-curve
2. TradingView. "Coppock Curve documentation." https://www.tradingview.com/support/solutions/43000589114-coppock-curve/
3. LuxAlgo. "Coppock Curve: Long-Term Momentum for Market Direction." https://www.luxalgo.com/blog/coppock-curve-long-term-momentum-for-market-direction/
4. The Robust Trader. "Coppock Curve Indicator." https://therobusttrader.com/coppock-curve/

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.