Coppock Curve Indicator: The Slow Monthly Signal Built to Catch Long-Term Bottoms

Most momentum indicators are built for people who check their screens every hour. The Coppock curve indicator is the opposite. It was designed for monthly charts, it fires very rarely, and its one job is to tell a long-term investor that a big decline in a stock index has probably run its course. If you have ever wished for something that ignores the daily noise on the Nifty and only speaks up after a real bear market, this is the indicator people point you to.

We’ll go through where it came from, the exact formula, a step-by-step worked example with numbers you can check on a calculator, and the honest list of things it gets wrong. That last part matters more than the formula.

What the Coppock curve indicator actually measures

Strip away the name and the Coppock curve is a smoothed momentum line. It takes two rate-of-change readings, adds them, and runs a weighted moving average over the result. Investopedia describes it as a long-term price momentum indicator meant mainly to recognise major downturns and upturns in a stock market index, and notes it is also called the “Coppock Guide”.

Its creator was Edwin “Sedge” Coppock, an economist by training. The sources disagree on the date it first appeared in Barron’s: StockCharts’ ChartSchool says October 1965, while Investopedia says 1962. Either way, it is a 1960s idea, and it was built for the S&P 500 and the Dow Industrials, not for individual stocks.

The odd bit is the choice of 11 and 14 months. According to ChartSchool, Coppock picked them because an Episcopal priest told him that was the average mourning period after losing a loved one. His theory was that markets need a similar stretch to recover from heavy losses. You can find that charming or unscientific (it is a bit of both), but it explains why the settings look so random.

The formula, piece by piece

Both sources give the same calculation:

Coppock Curve = 10-period WMA of (14-period ROC + 11-period ROC)

• ROC 14 is the percentage change between this month’s close and the close 14 months ago.
• ROC 11 is the same thing, but against the close 11 months ago.
• WMA 10 is a 10-period weighted moving average of the sum of those two.

The weighted moving average is the part people skip, so here’s how it works. ChartSchool’s example uses three periods: multiply the oldest value by 1, the next by 2 and the newest by 3, add them up, then divide by 6, which is 1 + 2 + 3. A 10-period WMA does the same with weights 1 to 10, so you divide by 55. The newest month counts ten times as much as the oldest one. That is deliberate. It lets the curve turn a little faster than a simple average would, without throwing away the smoothing.

If rate of change is new to you, our explainer on the rate of change indicator on NSE stocks covers the building block in more detail, including its quirks around big base effects.

The Coppock curve doesn’t tell you the bottom is in. It tells you, some months later, that the fall has lost enough steam to stop being the main story.

A worked example with monthly closes

Let’s build one by hand. The numbers below are hypothetical monthly closes for an imaginary index, not Nifty data. They were chosen to show a rally, a long slide and a recovery, because that’s the situation the indicator was designed for.

We need 24 months of closes: 14 months of history for the first ROC 14 reading, plus 10 readings for the weighted average. Month 1 closes at 10,000. The index climbs to 10,800 by month 6, then slides for most of a year to a low of 8,650 in month 15, and recovers to 10,400 by month 24.

Take month 15 as the first calculation. Fourteen months earlier is month 1, at 10,000. So ROC 14 = (8,650 / 10,000 − 1) × 100 = −13.50%. Eleven months earlier is month 4, which closed at 10,300, so ROC 11 = (8,650 / 10,300 − 1) × 100 = −16.02%. Add them and you get −29.52.

Repeat that for every month from 15 to 24:

The weighted products add up to −194.51. Divide by 55 and the Coppock reading for month 24 is roughly −3.54. Still below zero.

Sit with that for a second. In our made-up series the index is up about 20% from its month-15 low (10,400 against 8,650). The raw ROC sum flipped positive two months ago. And the Coppock curve still hasn’t given a buy signal. If you used a plain 10-month average of the sums instead of a weighted one, you’d get −12.80, even further from zero. The weighting is already doing its best to speed things up.

That is the indicator working exactly as designed. It waits for the recovery to be broad and sustained before it commits. The price you pay is that a chunk of the rebound has already happened.

How the signals are read

The classic rule is simple. On monthly data, a move from negative territory to positive territory is a buy signal. ChartSchool points out that Coppock himself only used it for buy signals. Many technical analysts later added the mirror image: a cross from positive to negative is treated as a sell. Investopedia frames it as three states: above zero means hold, a drop below zero means sell, a move back above zero means buy.

Because it runs on monthly bars, it barely ever fires. ChartSchool says that on its long-term monthly chart there had been only five signals since the late 1980s, with the first in 1988, after the 1987 crash. It also says a February 2001 sell would have avoided most of the 2000 to 2002 bear market, and a June 2008 sell would have got investors out before the plunge in the second half of 2008.

The record isn’t spotless, though. Investopedia’s example on the SPDR S&P 500 ETF notes that in 2016 the indicator gave a sell signal near the market bottom and then a buy signal a short time later at a higher price. So you would have sold low and bought back higher. That’s the kind of whipsaw a slow indicator is supposed to avoid, and it still happens.

Using it on Indian indices

Nothing in the maths is tied to the US market. You can put the Coppock curve indicator on a monthly chart of the Nifty 50 or the Sensex in any charting platform that offers it and read it the same way. A few practical points from how we’d approach it:

• Stick to broad indices first. The indicator was built for whole markets. An index averages away the company-specific shocks (a results miss, a promoter pledge, a regulatory order) that can drag a single stock’s momentum around for reasons that have nothing to do with the market cycle.
• Check the settings in your platform. The standard values are 14, 11 and 10 on monthly bars, so confirm your platform’s inputs match before reading anything into the line.
• Don’t expect frequent signals. On monthly data you may go years without a crossover. That’s normal, and it’s the point.
• Look at the slope as well as the zero line. A deeply negative curve that has started rising is telling you the decline is slowing, even before it crosses zero. It’s not a signal by itself, but it’s useful context.

It also pairs naturally with other long-horizon momentum tools. Martin Pring’s KST blends several rate-of-change speeds in a similar spirit, and our guide to the Know Sure Thing indicator shows how that one is put together if you want a second opinion from a different construction.

Faster settings for shorter timeframes

ChartSchool makes a fair point: since the Coppock curve is just a smoothed momentum oscillator, it can be used on intraday, daily or weekly data too. Shorter ROC settings make it faster and more sensitive; longer ones make it slower. Their example uses daily bars on the Nasdaq 100 ETF with a (20,10,10) setting, which ChartSchool says makes the curve a little less sensitive and may suit daily charts better. Their weekly Dow Industrials chart, as you’d expect, produced many more signals than the monthly version.

Our view: once you move to daily charts, you’ve turned it into a different tool. It becomes another momentum oscillator competing with MACD, RSI and the rest, and it loses the one thing that made it distinctive, which is its patience. If you want a fast signal there are better-known options. The Coppock curve earns its place on the monthly chart.

Change the settings enough to make the old signals look perfect and you haven’t improved the indicator. You’ve just described the past more neatly.

Where the Coppock curve falls short

Investopedia lists three problems, and all three are real:

• False signals. When the curve hovers near zero it can cross above and below quickly, pushing you to buy and then sell, or the reverse. On monthly bars each of those mistakes can cost months.
• Curve fitting. The default settings are fairly arbitrary (the mourning-period story makes that clear), and many traders tweak them until the historical signals look great. A setting fitted to the past may not give better signals in the future.
• Lag. With 10, 11 and 14-month look-backs, it will be late to flag major tops and bottoms. Our worked example showed it: a 20% rebound and still no buy.

ChartSchool adds a caution on divergences. More aggressive chartists sometimes watch for a bullish or bearish divergence between the curve and price to anticipate a crossover, but divergences don’t always lead to reversals. Sometimes the trend simply slows down and carries on.

We’d add one more, purely practical. Because signals are so rare, you can’t build much confidence in the indicator from your own experience. A handful of signals in a couple of decades is not a sample size. Anyone using it is leaning on the logic of the construction as much as on the track record, and should be honest with themselves about that.

Is it worth adding to your charts?

For a long-term investor who wants a rules-based nudge on when to stop being defensive after a major market fall, yes, it’s a reasonable thing to have on a monthly index chart. It won’t catch the bottom. It will usually confirm that the worst of the selling has passed, and it does so without reacting to every bad week.

For a trader, it’s a weak fit on its default settings, and once you speed it up it stops being special. If you’re still building your toolkit, our technical analysis guide for Indian stocks is a better starting point than any single indicator.

Quick recap

• The Coppock curve is a 10-period weighted moving average of the 14-period ROC plus the 11-period ROC, designed for monthly charts of stock indices.
• Edwin Coppock introduced it in Barron’s in the 1960s (sources give 1962 and October 1965), to find long-term buying points in US indices.
• A cross above zero is the buy signal; many analysts treat a cross below zero as a sell, though Coppock didn’t use it that way.
• It fires rarely, which is useful, but it lags, can whipsaw near zero, and its settings are easy to over-fit.

Disclaimer: This article is for educational purposes only and is not investment advice. The worked example uses hypothetical prices for an imaginary index. Trading and investing involve risk of loss, so speak to a SEBI-registered adviser before making investment decisions.