Recently studying technical indicators, I found that the Bias Divergence Rate (BIAS) tool is quite practical, especially for judging overbought and oversold conditions. Sharing my understanding and operational insights.

The divergence rate actually measures how much the stock price deviates from the moving average line, expressed as a percentage. Simply put, when the stock price deviates too far from the trend line, the chances of a rebound or pullback increase. A positive divergence rate indicates the stock price is above the moving average, while a negative divergence rate is below.

The calculation method is as follows: N-day BIAS equals the closing price on the day minus the N-day moving average, divided by the N-day moving average. It looks complicated, but it’s basically about observing the position of the stock price relative to the moving average.

Regarding what setting for the divergence rate is appropriate, many people have questions. First, choose the period of the moving average: short-term commonly uses 5-day, 10-day, 12-day; mid-term uses 20-day, 60-day; long-term uses 120-day, 240-day. Then, select parameters based on your trading style; common choices are 6-day, 12-day, 24-day.

My personal experience is that shorter periods make the indicator more sensitive, easier to catch short-term opportunities, but false signals are more frequent. Longer periods are the opposite—more stable signals but slower to react. Adjust this based on the activity level of the stocks you trade and overall market sentiment.

In actual operation, set a positive and a negative threshold as parameters. For example, for 5-day divergence rate, try setting around 2% to 3%, but this number should be adjusted based on historical data and your experience. In highly volatile markets, divergence rates may frequently exceed thresholds, so flexible adjustment is important.

The buy and sell signals are as follows: when BIAS exceeds the positive parameter, it indicates overbought, consider selling; when BIAS falls below the negative parameter, it indicates oversold, consider buying. But don’t rely solely on this indicator; it’s better to combine it with the divergence rates of the 5-day and 20-day moving averages to get a more comprehensive view of short-term and medium-term trends.

Another important aspect is observing divergence. If the stock price hits a new high but the divergence rate doesn’t reach a new high, it could be a top signal; conversely, if the stock hits a new low but the divergence rate doesn’t reach a new low, it might be a bottom signal.

However, divergence rate also has limitations. If a stock’s long-term rise or fall is very small, the divergence rate’s effectiveness is limited. It also has a lagging nature, which can cause missed opportunities, so it’s useful as a reference for buying but should be used cautiously for selling. The effectiveness varies with market capitalization—large-cap stocks tend to be more stable and accurate, small-cap stocks less so.

In practical trading, I usually combine divergence rate with the KD indicator or Bollinger Bands for more accurate judgment. Parameter selection is crucial—too short a period reacts excessively, too long a period is sluggish. Stocks with good performance and low risk rebound quickly during declines, while poor-performing stocks rebound slowly. So, the divergence rate setting should be flexibly adjusted based on the specific asset.

Overall, BIAS is a simple and intuitive tool, but it shouldn’t be relied on alone. It’s best to combine multiple indicators and consider actual market conditions for comprehensive judgment.