Recently, a question has been asked many times: how large is the deviation rate considered significant? Actually, this seemingly simple question involves the success or failure of the entire trading strategy.

To start with the conclusion, there is no absolute definition of what constitutes a "large" deviation rate. After so many years in the market, I’ve seen too many traders blindly apply a fixed value, only to get slapped in the face. The real secret lies in understanding the relationship between price and moving averages, and then judging based on the asset you are trading.

The core logic of the deviation rate is quite straightforward: it measures how far the current price deviates from the average cost. The formula is (closing price of the day minus the N-day moving average) divided by the N-day moving average, multiplied by 100%. A positive result indicates the price is above the moving average (premium), while a negative result indicates it’s below (discount). The larger the number, the farther the deviation.

But here’s a key point: deviation always exists. Because moving averages are inherently lagging, when the market moves rapidly, the moving average can’t keep up with the price, making deviations inevitable. The focus isn’t whether there is deviation, but to what extent it is considered “excessive.”

Based on my practical observations, for major indices like the S&P 500, what deviation rate is considered large? Around -3% to +5% is when you should start to be cautious. Cryptocurrency markets are more volatile; Bitcoin’s extreme values are usually in the 8% to 10% range. Gold and other precious metals are relatively stable, with 2% to 5% considered quite extreme. But these are just references; each market and asset may differ.

My advice is, before using deviation rate for trading, you must backtest your asset. Look at the past year to see what ranges the deviation rate most frequently fluctuated within, and when extreme values appeared. Only then can you determine what constitutes a large deviation rate for your trading target.

In practice, whether a deviation rate is large also depends on the context. If it’s just an isolated extreme value, I usually don’t act immediately. But if it’s combined with divergence signals, it’s a different story. For example, if the price hits a new high but the deviation rate doesn’t confirm the new high (top divergence), that’s a clear warning signal. Conversely, if the price hits a new low but the deviation rate doesn’t (bottom divergence), it’s often a precursor to a rebound.

Parameter settings also influence judgment. Short-term traders might use 5-day or 10-day moving averages, swing traders might use 20-day, and long-term investors might use 60-day. Different moving average parameters mean different thresholds for extreme values. So, the same deviation rate value can have completely different implications on different timeframes.

I’ve seen many make the mistake of mechanically entering trades when they find a deviation rate they consider large. When a strong trend kicks in, prices still run wildly in one direction, and the deviation rate becomes more extreme. Their stop-losses get hit one after another. That’s why I say deviation rate should only serve as a warning indicator, not a buy or sell signal.

The correct approach is this: first, determine what deviation rate is considered large for your asset. Then, when approaching extreme values, raise your alertness. Combine this with other signals like candlestick reversals, RSI entering oversold zones, etc., and consider scaling into positions gradually. Never go all-in at the first sign of an extreme value; markets sometimes like to push further in the same direction before reversing.

Another key point: in strong trending markets, the deviation rate tends to become less responsive. That is, even if the deviation rate is already extreme, the price may not immediately revert to the mean. Instead, it might consolidate sideways before starting a new trend. In such cases, multiple confirming signals become even more important.

Finally, I want to say that the question of “how large is a large deviation rate” has no standard answer. It depends on your trading style and the characteristics of the asset. Spending time to backtest and establish your own judgment standards is much more reliable than blindly applying someone else’s fixed values. Indicators are just tools; the trend is the main focus. Keep this in mind, and your trading will avoid many detours.