Have you ever watched an ASX heavyweight plummet on a slight earnings miss or a sudden spike in market panic, only to bounce right back to its normal trading range a few days later?
That is the “rubber band” effect in action. But in technical trading, it’s more commonly referred to as mean reversion.
Mean reversion is the financial theory suggesting that asset prices will eventually return closer to their long-term average (the “mean”). Think of a stock’s price like a rubber band stretched around a moving average. The further the price stretches away from that average in a short amount of time, the greater the tension becomes. Eventually, the tension gets too high, and the price snaps back toward the middle.
For traders and investors, spotting these extreme stretches presents higher probability opportunities to capitalise on market overreactions. But you can’t just guess when a stock is stretched too far. You need the right technical tools.
Bollinger Bands (Seeing the Stretch)
Bollinger Bands are a fantastic visual tool for identifying mean reversion setups. The indicator consists of three lines:
- The Middle Band: Usually a Simple Moving Average (SMA). This is your “mean.”
- The Upper Band: Two standard deviations above the SMA.
- The Lower Band: Two standard deviations below the SMA.
Statistically, about 95% of a stock’s price action should occur between these bands. When a stock’s price suddenly pierces the outer bands, it tells you the rubber band is stretched to its absolute limit. If BHP suddenly drops and the daily line/candle closes entirely below the lower Bollinger Band, the stock is historically undervalued in the short term, signaling a potential reversal opportunity.
The RSI (Confirming the Tension)
You never want to rely on just one indicator. To confirm the Bollinger Band signal, traders can use the Relative Strength Index (RSI). The RSI measures the speed and change of price movements on a scale of 0 to 100.
- Oversold (Under 20): If the RSI drops below 20, it indicates the stock has been sold off too aggressively.
- Overbought (Over 80): If the RSI pushes above 80, it means buyers have driven the price up too fast, and a pullback is likely.
When you see a stock pierce the lower Bollinger Band and its RSI drops below 20, you have a good indication that the market has overreacted to the downside.
Don’t catch falling knives
While mean reversion is powerful, markets can remain irrational longer than your account can remain solvent. A stock trending strongly downward can stay “oversold” for weeks.
To protect your capital, never enter a trade just because the indicators say a stock is stretched. You must wait for price action confirmation. This means waiting for the stock to stop falling, form a bullish reversal, and begin pointing back toward the moving average before you enter the trade.
Trading the rubber band effect requires patience and strict risk management, but when executed correctly, it is a great short-term strategy for trading the ASX.